S 679 
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Clearing- Land ^ Rocks 

ior 

Agricultural and 
Other Purposes 



By J. R MATTERN 



Published by 

The Institute of Makers of Explosives 

Room 902, io3 Park Ave., New York 



Clearing Land of Rocks 

for Agricultural and 

Other Purposes 



By J. R. MATTE RN 



Published by 

The Institute of Makers of Explosives 

Room 902, 103 Park Ave., New York 



Copyright, igi8 
By Institute of Makers of Explosives 






INSTITUTE 

OF 

MAKERS OF EXPLOSIVES 

Organized July 15, 1913 

MEMBERS 

AETNA EXPLOSIVES COMPANY, Inc. 
New York, N. Y. 

ATLAS POWDER COMPANY 
Wilmington, Del. 

AUSTIN POWDER COMPANY 
Cleveland, Ohio 

E. I. DU PONT DE NEMOURS & CO. 
Wilmington, Del. 

EGYPTIAN POWDER COMPANY 

East Alton, 111. 

EQUITABLE POWDER MFG. CO. 
East Alton, 111. 

EXCELSIOR POWDER MFG. CO. 
Kansas City, Mo. 

THE GIANT POWDER CO., Cons. 
San Francisco, Cal. 

THE GRASSELLI POWDER CO. 
Cleveland, Ohio 

HERCULES POWDER CO. 
Wilmington, Del. 

ILLINOIS POWDER MFG. CO. 
St. Louis, Mo. 

KING POWDER COMPANY 
Cincinnati, Ohio 

MONONGAHELA POWDER CO. 
Fairmont, W. Va. 

SENIOR POWDER COMPANY 

Cincinnati, Ohio 

STANDARD POWDER CO. 
Philadelphia, Pa. 

UNITED STATES POWDER CO. 
Terrfci-Haute, Ind. 

MAY 24 1918 




How weeds and briars grow up about a boulder in a field. In this case the stone itself is not very 
large, but the total land area put out of business is three times as much as the stone covers. 



INTRODUCTORY 

THIS bulletin is published by the Institute of Makers of Ex- 
plosives. The aim is to give the united conclusions and the 
sum of the experience to date of nearly all makers of explosives 
and of farmers who have dealt successfully with the problem of 
boulders and ledges in their fields. 

The material has been classified and assembled so any phase 
of it will be available easily and quickly. Uncertainties have been 
eliminated as much as possible in favor of known facts and formu- 
las established by actual experience. It is offered as a manual or 
handbook for farmers, home and road builders, contractors, park 
makers and others who must remove rocks from land, and as a 
textbook for students of agriculture. 

Readers will find that the recommendations are impartial, and 
that the suggestions on that part of the work which can be done 
best with explosives are particularly complete. 



Boulders and Ledges of Rock 

Eight generations of farmers have picked stones off the fields of a great 
many farms in this country, and in these same fields all the boulders too big 
to be moved by the direct strength of men and horses still arc dodged by the 
present farmers. Some land cleared and farmed as long ago as the Revolu- 
tionary War has not had the "niggerheads" removed to this day. 

Those stones that project above the surface of the ground can be avoided, 
but those hidden underneath are more serious trouble makers. The man who 
works his own land for years gets to know where they lie, and can escape them 
to a certain extent, but it is by broken plowshares that a new plowman learns 
their location. 

In former years, before the value of land began to increase as it has of 
late years, farmers found more profit in locating a new acre that had fewer 
stones or none at all than in removing those from a stony acre. But that time 
is past. Farm land today can be made to pay without removing the boulders, 
but not the full hundred cents from each dollar earned by the work and ex- 
pense put on it. Stony farms can be sold, but not for big prices. Thoughtful 
farmers remove the rocks. 

It is surprising how much there is to know about the disposal of boulders. 
Too often this work has been attempted in ways that were crude and wasteful 
of energy and time, and considering these items, very expensive. This is partly 
due to the lack of published data describing easier, simpler ways. The up-to- 
date farmer will not tolerate methods that are wasteful or unprofitable. He 
may find the information he wants in the following pages. 



The Profit and Loss Account of Boulders 

The interference of boulders and rock ledges with farming operations and 
profits takes many forms, and its cost can be estimated from a glance at a few 
of them. 




This is the sort of perpetual tenant which pays no rent, and on which this bulletin declares war. 

4 



On ground where a cultivated crop is grown, each boulder causes the 

waste and loss of about half an hour per year of the time of a man with a team, 

worth five dollars a day. Four seasons' loss will remove the 

Time Lost . stones. They ",eat their heads off" as the saying goes, ten or 

more times during the active lifetime of the average generation. 

In addition, the breakage and damage to tools and machines may amount 
to as much in total loss as that from waste of time. This is particularly true 
of those farms where modern heavy implements are used, as, for instance, the 
heavy disc harrows for four or more horses, the gang plows, and all the tillage 
tools pulled by traction engines. Tractor plows and harrows are sure to be 
broken in stumpy or rocky land. It is impossible to make good time with gang 
plows or harrows among boulders, because of the constant stopping necessary, 
and besides, the work done is bound to be poor. Ten to twenty boulders to 
the acre are just about as bad as 100 for the man with the engine imple- 
ments — they make good work and speedy work impossible. 

About each rock that sticks above the surface some weeds are sure to 

grow. There never is the stone, or log, or stump, on or in 

Weed Breeding the ground but where you can find a thistle or two, or 

several specimens of other equally noxious plants, growing 

close to the edge or out from under it. These single weeds re-seed entire fields. 

Another feature of the loss sometimes caused by tight stones in fields is 
the injury to horses and men caused by the sudden strain and jerks. Horses 
sprain leg joints, shoulders, hips and backs. Many 
Danger to Horse spavins have their beginning in the ugly twists sustained, 
and Men Brood mares often are caused to lose their foals prema- 

turely. The baffling for which stones are responsible is 
one of the most common causes of balkiness of farm horses. A team can be 
ruined in a short time by such treatment. 

The danger to men is not so common, but when it does come it comes 
heavily. The records of the past generation show that many a farmer was 
struck with a plow handle when the plow point encountered a stone that was 
tight. Sometimes the result is a broken arm or hip, or rib, or worse still, a 
rupture. The newspapers frequently report accidents caused by the driver of 
a mowing machine being thrown from the seat into the knives, or under the 
heels of the horses, when the machine suddenly struck tight obstructions such 
as stones. 

The direct loss of crops which would grow on the land occupied by the 
boulders need not be stated in figures. Every farmer knows that the loss of 
corn, wheat, or hay on a square rod amounts to 1 5 to 50 cents a year. 

Tight stones on a farm are bound to keep its selling 
Low Land Value value down. One of the first things a shrewd buyer of 
and Increase land will want to know is whether the soil is free of rocks 

that interfere with cultivation. One of the easiest and 
surest ways of increasing the value of land, for selling, for actual use, and in 
the estimation of other people, is to clear away the boulders. 

The stones themselves may not be without value when they are broken up 
in pieces small enough to handle. It is well for every farm to have a pile 
in seme convenient place, where they can be had any 
Value of Stones time they are wanted. They are valuable for building 
material, and in drains and walks. At the rates prevail- 
ing in many places it is easy to collect fifty dollars' worth of stone right 

5 



near where it Is needed and save both the cost of the stone and most of the 
expense of hauling. 

Some of the more common purposes for which stones are valuable on farms 
are for blind drains, for lining ditches along roads or in fields, where the water 
gouges out the sides or bottom on account of a grade or turn, for road founda- 
tions, for repairs to walks, for constructing steps, chimneys, walls, etc., for fill- 
ing in concrete construction, and for building garages, houses, barns and silos. 

Clearing land of boulders should not be regarded as an expense, like taxes, 
or like the cost of shoes to wear. It is an investment, like the purchase of 
Government bonds, or like the purchase of shoes by a storekeeper, to sell 
again. When money is spent for removing boulders by a farmer, he is buying 
something — the clean land — that at once begins to pay back the cost of the 
work. It pays for itself within three or four years and then keeps right on pay- 
ing dividends year by year. 



Kinds of Rock and Their Nature 

It helps if you know your rock when you go to break it up, for many 
different kinds exist as boulders and ledges on farms and in roads. In some 
sections the term "hardhead" is used to describe one kind of boulder. Another 
term is "niggerhead." It is better to know the rocks by the names which 
designate their real nature. 

Rock Qualities 

What does make a difference is that some stones are easy to break and 
others are not. To understand why, a study of the stones is necessary. Their 
resistance depends on their comparative hardness and toughness. These two 
qualities must not be confused, for they are not the same. 
Hardness and To illustrate, window glass is hard, but not tough. It will 
Toughness scratch very hard steel, but will shatter under a light blow. 

Untempered iron is tough, but not hard. It can be ground 
away rapidly by a stone, or scratched with glass, but it is extremely difficult 
to break by pounding or twisting. 

To some extent stones possess the same qualities, and in addition almost 
all of them have one or more lines of weakness. Most rocks have a grain, not 
unlike the grain of wood, and will split more easily along the grain, and less 

easily in any other direction. It is 

safe to say that all rocks have 
joints running in one direction, and 
some rocks have two sets of joints 
running at right angles. The joint 
lines may not be visible, but the 
force of a blast or of a sledge will 
find them. There is still another 
sort of weakness in rocks with 
which the blaster should be famil- 
iar. This is the bedding plane, 
or layer — with lines running at 
right angles to both joint-lines 
mentioned. 

Some knowledge about the 
joints and natural cleavage planes 
makes the breaking of rocks easier. 
Even the most massive rocks are 
divided into blocks of varying sizes, 
making them split in some direc- 
tions easier than in others. The 
cracks will tend to stop short and 
splinter out or to run entirely 
through the stones, depending on 
the toughness of the rock, while 
the blocks will or will not crumble 
much according to their hardness. 

Description of Rocks 

In these brief remarks we will make no attempt to give the geological 
classification of the rocks, but will try to identify the typical rocks found as 
boulders and ledges by names which are used most generally, and to make 

7 




How the seam and joint lines crisscross in most 
stones. A little inspection of a stone nearly always 
will show a spot where the force can be applied to 
break it with much less force or greater effectiveness 
than if the stone is attacked at solid spots. 




Two fields which will cost $50 to $200 or more an acre to clear of stumps and stones. If the land 
can be used for residential purposes or for some form of intensive farming like trucking or fruit growing, 
it will pay to clear such places, but it will not pay to clear them for general farming and pasture purposes. 



clear their nature. Common names for different kinds of rock or stone are 
not always satisfactory because the common name applied generally to one 
kind of rock in certain localities in numerous instances is applied to an entirely 
different kind of rock in other localities, but it is hoped that any confusion 
will be limited. 

These three classes of rock seldom exist as boulders, though they some- 
times interfere with cultivation in the form of ledges close 
Talc, Gypsum to the surface of the ground. In this shape they nearly al- 
and Shale ways are full of two sets of joints, and lie in thin beds. Some- 
times the seams are so close together that the rock breaks 
up into blocks only an inch or two square. They are fairly tough, are inclined 
to crumble rather than split or crack, when struck with a sledge hammer, and 
are easy to drill. 

Usually takes the form of flat boulders on the surface in fields or of ledges 
which project almost to the surface or above the surface several 
Limestone feet. Limestone generally has two systems of joints. It also has 
bed lines wide apart — a foot or more. This kind of stone nearly 
always is tough, breaking off, rather than splitting far. Its hardness varies. 
The boulders of this class frequently are nearly round. Slate rock is char- 
acterized by a thin shingle structure. The leaves are less than a quarter 
Slate of an inch thick. There are joints as well. The stone is tough, break- 
ing only a short distance (but splitting on cleavage lines easily), soft, 
and inclined to crumble. 

Occurs as boulders of every shape and size, and as ledges of all sorts. The 
ledges usually are stratified — that Is, in beds of a thickness of one, 2, 3 or more 




See picture on preceding page 



feet. It has frequent joint lines running in two directions, and it breaks up 
into irregular sized blocks of more or less rectangular shape. The 
Sandstone sand particles which compose the stone are very hard. When 
the cementing material is silica the stone is blue or white, and 
much harder than when of an iron origin, making a brown or red stone. For 
purposes of drilling, blue sandstone must be classified as a hard rock, and 
brown sandstone as softer rock; and for breaking purposes, both kinds may be 
listed as soft. It crumbles easily, and is rather tough. 

These rocks and others like them in structure lie 
Lava, Mica Rocks, in layers from 2 to 100 feet thick. They have no 
Feldspar other bed lines, but they have infrequent joint lines. 

Lava, excepting that of the pumice type, is hard and 
brittle. The boulders split fairly easily into pieces of irregular shape and size. 
A mixture of various rocks, such as slate, sandstone and the like, often in 
the form of pebbles cemented together, making a rock that lies in beds. It 
may be crystalline and very hard — even flinty — or it may be 
Conglomerate only medium hard. The boulders are rather brittle than 
tough. Joints in one direction are located wide apart. Boul- 
ders of conglomerate rock sometimes have a ball-like structure, with layer 
after layer 1 to 6 inches thick, and joints every 2 to 4 inches. The layers of 
such rock crack off like the skin of an onion. 

Occurs often as boulders, though frequently there are granite 
Granite ledges. Granite is of a layer structure, with frequent joints. It 
splits easily. It is not particularly tough, and is hard to drill. Some 
granite breaks easily while other is difficult to shatter. 



These rocks are very different and can only be classified together when 

referring to methods of breaking them. They 

Marble and other hard, are fine-grained, and have no distinct bedding 

tough rock, such as planes. They do not break up in layers. They 

Quartz, Trap, Porphyry do break along joint lines. They are sometimes 

quite hard, but not very tough, and except trap 
rock, which is tough, often shatter easily. The boulders are numerous in some 
sections of the country, and ledges are not infrequent. 

Seme rocks are full of irregular cavities resembling 
General Features bubbles, and these generally make the breaking easier. 
The cavities interfere with the regular joint lines and 
cause the splitting to take place along new lines of weakness. 

The amount of force required to break a rock depends on its hardness and 
its relative toughness, and on the lines of weakness or cleavage which run 
through it. Hard rocks usually crumble less easily than soft rocks, but generally 
split better when once started. Tough rocks are hard to split into small pieces, 
while brittle ones shatter to bits under a proper blow. 

The point at which the force should be applied for the most and quickest 
breakage depends on the structure of the rock and the direction and frequency 
of bedding and joint lines. 



10 



Eight Methods 



Methods of Clearing Away Rocks 

Rocks too large to be pried out and loaded for hauling by hand, and tight 
ledges, must be broken. Following is described eight methods of breaking them. 
Each method has advantages under certain conditions, but some are much more 
serviceable, convenient and easy than others under most circumstances. 

List of Methods 

Hauling: Consists of either dragging with chains or 
loading on sled or wagon. See page 31. 

Sledging: Consists of hammering them into pieces 
small enough to handle. See page 14. 

Burying: Needs no description. Seepage 14. 

Breaking with fire: It is possible to break many kinds of rocks in this 
way. See page 14. 

Plug and feather breaking: Intended for splitting out building stone. 
Consists of drilling a series of small holes in a line across a boulder, and then 
driving into these holes special steel wedges. 

Blasting by drilling: Called "blockholing" when referring to boulders. 
See page 23. 

Blasting by undermining or underdrilling: Called "undermine blasting" 
or "snakeholing." See page 19. 

Blasting by mudcapping: Also called "doby shooting," "plastering" or 
"blistering." Seepage 15. 

Choice of a Method 

In the practical handling of rock clearing, the elements 
to be considered are the costs of labor and material re- 
quired. These are governed by the nature and amount 
of rock to be broken. Time is also an important factor. 
The softer and more brittle boulders, if they are not large, may be dis- 
posed of by any of the above methods. Very hard and tough rock cannot be 



Cost, Men, Time 
and other Factors 








How a boulder can mar the appearance of a farm from the roadside view. Such a stone leads possible 
buyers of a place to think that the field contains many such. 



'■■rrmr. 1' *'')|fV«pipa[?^ 




The disposal of this partly buried boulder called for rolling it out of its bed in the ground without 
breaking it, and then mudcapping it. It was rolled out with one stick from the position shown in the 
first picture, and (see next page) 



sledged into pieces successfully. When such rocks are to be blasted they should 
be drilled (blockholed) rather than mudcapped or undermined. Ledges of rock 
always should be broken up by blasting drilled holes. The limits of size of rock 
at which mudcapping becomes impracticable are explained on page 1 5. 

Labor conditions are important. On some farms men are very scarce and 
wages are high. At other places there are periods when laborers are practically 
idle and can be put to disposing of stones, without much extra cost. In the 
former case it is wise to let explosives do all the work possible with no more 
drilling, sledging, handling and hauling than absolutely necessary. In the 
latter case the amount of explosives used should be kept down, and the idle 
men left to do the resulting extra work. 

The time element is equally important. If nothing else demands the at- 
tention of the men on the farm, a slow method is all right, but when stones must 
be removed in a hurry, the quickest method probably is the cheapest in the end. 

When the cost must be kept down as much as possible, and when easier 
and better methods are not available, burying and breaking by fire may be 
resorted to, provided there is labor available at little cost. Sledging, when 
practicable, is a cheap method if labor and time are not considered, provided 
good sledges are available. But it is slow, hard work. This applies to any 
way of disposing of rocks except blasting. If the conservation of energy 
as well as of time and men is desirable, the use of high explosives is the only 
method to consider. 

Mudcapping is the easiest way to blast boulders in most instances, but 
takes the most explosive of the three blasting methods. It seldom should be 
attempted with boulders containing more than 15 cubic yards of stone unless 
they are thin slabs, and is expensive with trap rock or other very hard and 
tough material. Rocks should be flat rather than round, or at least should have 
a flat side on which the charge can be placed. 




mudcapped a few days later with five sticks with the result shown in the second picture. Note 
that the entire rock has been reduced to small fragments requiring no further handling. 



Undermining or " snakeholing " has practically the same effect as mud- 
capping, though it requires less explosives and, usually, a little more work. 
Blockholing, though effective and economical, requires time and tools to drill 
the holes. 

Mudcapping and undermining are pre-eminently the methods to use 
where there are only a few boulders to dispose of, since one man can 
do in an hour by these methods what it would take much longer to do 
by any other method. Stones that are deeply imbedded should be under- 
mine blasted lightly to roll them out, or at least to loosen them, before they are 
mudcapped. Some very large stones should be both undermined and mud- 
capped, with two or more charges fired simultaneously with an electric blasting 
machine. 

Other combinations of methods will suggest themselves to a resourceful 
blaster. 

Study the rock. If it is imbedded, roll it out by undermine blasting as 
above directed, and examine it on all sides. Usually you will find that an 
undermined or mudcap blast, unless the charge of explosive has been small, 
will break up the boulder and make blockholing unnecessary. 



13 



Detailed Directions for Disposing of Boulders 

Small boulders, weighing only 100 pounds or so, may be dug out and rolled 

into wagons on planks, or dragged off the field with chains. With 

Digging Out larger stones, hauling is slow business, and is likely to result in 

injury to men. The hard straining required to lift the rocks, 

added to the danger from the falling of heavy stones, makes what would seem 

to be one of the simplest and safest of jobs an exceedingly hazardous one. 

A practicable method of disposing of rocks is to break 
Sledging Rocks them up with sledges. Use heavy sledges -the heavier the 
better. 1 he tough rocks are almost impossible to break in 
this way. It is impractical to sledge up large rocks of any kind. 

Pay particular attention to the direction of the grain and the lines of 
cleavage. A blow right at a vital point often will break a rock in two when 
you could hammer away an hour at another part without much effect. 

When you sledge rock, there is much danger from flying bits of stone, and 
it is a good plan to wear gloves. Tie your coat sleeves over the gloves or the 
gloves over the sleeves, turn your collar up, wear a cap which pulls down over 
the ears, and wear goggles. If you have no goggles, be careful to shut your 
eyes when striking the rock. 

One way is to dig a pit alongside the stone, and tip it over. This is suit- 
able for stones that can be pried over. Large stones must 
Burying Rocks be undermined and let sink down slowly. Let each end 
down separately. Extreme care must be used in this oper- 
ation to prevent the rock from rolling on the man who digs. Burying heavy 
stones is a dangerous operation, and has crippled and killed many a man. 

Burying rocks is open to the objection that at some time the work may 
have to be done over again, on account of not getting the top low enough. 
Frost, erosion, and other forces gradually have the effect of bringing the stones 
to the surface. If the rock is large, it will interfere seriously with the growth 
of anything planted over the spot. Buried stones are beyond your reach if 
needed for building purposes. 

Dig a trench round the stone to be broken, as deep as the stone goes, or 
somewhat deeper. Gather a cord or two of wood to start with. Have plenty 
of large pieces^logs and the like. Build your fire, and see that it gets intensely 
hot. After it burns four or five hours, and the stone is thor- 
Fire Breaking oughly heated all through, suddenly draw away the fire and 
throw on several buckets of cold water. It will snap and 
crack. Pieces will shell off the surface. Rake these away and renew the fire 
for another several hours, and repeat the water application. Gradually you will 
be able to wear the rock down and crack it entirely through. After two or 
three of such burnings you will be able to pry open the cracks that are formed 
and sledge up the remaining large pieces. 

Be careful to keep out of the way of flying fragments when you throw on 
the water. Stones also often break with a loud crack when the fire gets very 
hot. See that none of the pieces strike you. In addition to their force, they will 
burn like melted iron, for they are almost red hot. One small piece in your 
eye may destroy the sight. 

The easiest way of breaking stones is to do it with high ex- 
Blasting plosives. The directions for this work are given in full detail, with 
careful attention to mudcapping, blockholing and undermining or 
"snakeholing," and to combinations of these. In order to do the matter justice 
it is placed in a separate chapter. 

14 



Blasting Boulders and Ledges 

All of the methods described in the preceding chapter are more or less 
useful, but in actual practice the disposal of boulders or ledges nearly always 
will be impractical unless you use explosives. 

Mudcapping Rock 

Briefly, mudcapping rocks consists in placing the explosive in a neat pile 
on a face of the rock, covering it with about 6 inches of stiff wet clay, and ex- 
ploding it. When done right, the force of the explosion breaks the rock. 

It is the enormous speed of the gases which accounts for the success of 
such a blast — the time element. Mudcap blasting is made possible by the 
intensely fast shattering action of some of the modern high explosives. It can- 
not be done satisfactorily with black powder nor with the slower kinds of high 
explosives. 

Owing to the resistance of the air and the inertia of the material in the 
mudcap, the gases strike the rock like an enormous sledgehammer swung at a 
rate faster than the eye could follow. Such a blow, if in proportion to the size 
and strength of the stone, is sure to shatter it. 

Of the three distinct methods of blasting, mudcapping is 
Description the best one to use when the boulders to be broken are flat and 
brittle and smaller than 5 or 6 feet across. 

Probably the most economical mudcapping per cubic yard of rock is in 
blasting sandstone boulders having flat sides, and containing 4 to 6 cubic yards. 
Some sandstone is brittle, yet hard to drill, therefore should be broken by mud- 
capping. Shale, slate, conglomerate and other such rocks break very success- 
fully under mudcap blasts. Mudcapping is less satisfactory, owing to greater 
quantity of explosives required, when very hard and tough rocks such as trap, 
etc., are to be broken. In fact, mudcap blasting had better not be attempted 
on hard, tough rocks that are more than 3 feet in diameter unless no drills are 
to be had, and the stone must be removed immediately. 

If the stone lies free on the surface, it is ready for the placing of the ex- 
plosive. If it is buried in the ground more than a foot, it is a good plan to dig 
or blast away the dirt before attempting the mudcap blast. One way to do 
this is to dig a trench round the stone, to within a 
Preparing the Rock few inches of its bottom. Another way is to place 
one or more small charges down alongside the stone 
and to loosen up the dirt or throw it away from the sides, but in such a way 
as to leave the ground firm and undisturbed underneath. A third, and probably 
the best way where the stone is almost buried, is to explode a slightly larger 
charge down under one side of the stone to roll it out of its bed, and onto the 
surface of the ground. Then it is ready for mudcapping. 

In determining the best point at which to place the explosive, considera- 
tion of the principles of rock structure, as outlined on pages 7 and 9, should 
be the basis. Study the make-up of the rock and de- 
Locating the Place termine the directions in which it will split the easiest. 
for the Charge Look for and work for the hair-thin but far reaching 

seams. Clean the dirt or dust from likely-looking 
places. The joint lines most of the time will be hardly visible, yet they are 
important if the most complete and economical breaking is to be secured. 

Some workers say that they put the explosive where they would hit the 
stone with a sledge if it would be possible to break it with one blow. The big 

15 



thing is to get the explosive at a vulnerable point on the rock, whether this is 
top or sides. It may be necessary to support the explosive and its covering of 
mud with a banking of dirt, or with props from the ground, if the charge has 
to be located down along the side. 

It is better to place the explosive in a depression or hollow on the stone, 
or at least on a flat face, than on a round or bulging surface. A round face 
acts to some degree as an arch, and resists the blow of the explosive much more 
than a flat face. A depression gives the explosive some confinement that en- 
ables it to do better work. 

In placing the explosive it sometimes is well to deepen crevices or de- 
pressions with a drill or cold chisel, in this way making what might be called 
a semi-mudcap out of the blast. Such a blast is more efficient than when the 
explosive is placed on a flat or rounding surface. If it is desired to break the 
boulder or rock into pieces of certain shapes and sizes, make channels across 
the face with a chisel or mason's hammer and place the explosive in these 
channels. The process is like breaking ice by chopping channels across it. 
This treatment gives rough dimension pieces, but it may increase cost. 

The charge of explosive ordinarily should be placed in a low cone at the 
point selected on the rock. If less than four sticks are to be used, it is well 
to take all the explosive, except ^ 2 stick for priming, out of the paper wrapping 
and press it into place. If the charge is large, one or 
Putting the more of the sticks can be left intact and bedded in loose 

Charge in Place explosive. Sometimes the sticks bed-in better when cut 
in two. The explosive should not cover much area on 
the stone, since widely spread charges tend to distribute their force and have 
lower breaking ability. Sometimes it is a good plan to place the explosive in a 





How a mudcap charge is pressed down on a flat side of a boulder, with fuse projecting from the mud, and 
how a boulder is broken up. This charge was placed properly and was of the right amount. Note that none of the 
pieces were thrown far, though the stone is well broken up. 

16 



long, narrow mass— if there is a long depression, or crack, or the rock is much 
longer than it is broad. Thin edges of the mass should be pressed in and made 
steep and square. 

Before all of the charge is in place, put in the cap with fuse or the electric 
blasting cap. See pages 34 and 41. The best way is to prime a part of 
a stick of explosive in the usual way and bed this in the 
Inserting Cap loose explosives. If you decide to do this, stand the primed 
powder on end, with fuse or wires projecting from the top, 
and the closed end of cap pointing toward the center of the whole charge and 
then press the rest of the loose explosive about it. 

If a primer of this kind is not used, the cap must be inserted directly in 
the charge. To do this punch a hole a little larger round than the cap about 
one-third of the way down in the top of the charge. The cap should be in the 
upper third of the charge. To place the cap deep in the mass might lower the 
efficiency of the blast. 

Use the handle of the cap crimper or a blunt-pointed stick for punching 
the hole, as directed on page 38, and see that the cap is pushed to the bottom 
of the hole and that the explosive is pressed closely around it. 

The covering of mud should be put over the charge carefully. Be sure 
that the cap is not pulled out of the explosives during the covering operation, 
or later. 

The mud cap should be, preferably, of stiff wet clay. If clay cannot be 
got conveniently, use the heaviest earth you can find. 
The Mud Covering Sand is the least satisfactory material, but can be 
used if made thoroughly wet. In any case, the mud- 
cap must be MUD and not dust. 

At least 6 inches of mud cover should be placed over the explosive. This 
means 6 inches of covering in all directions over all of the charge. If the charge 
is 6 inches broad, then the mudcap would cover at least 18 inches of the rock, 
with the charge centered under it. To make a mudcap when the surrounding 
ground is dry, it is a good plan to gather and mix the mud in an old dishpan 
or box. Then to apply it on the rock simply turn the pan or box over at the 
right place and press the mud down so that no possible air spaces remain be- 
tween it and the explosive or the stone. Be careful that there are no stones 
in the mud covering. They fly like bullets when the charge is fired. 

The amount of explosive to use depends on the size and shape of rock and 

on its toughness and hardness. Below is a table which will serve to guide the 

blaster. These figures should be high enough to 

Amount of Explosive cover tough stones. Less explosive may be used 

for rocks that are easier to break. Rocks smaller 

than one cubic yard require more explosive than their size-proportion. 

Approximate Number of Pounds of Explosives Required for 
Mudcapping per Cubic Yard of Rock 

Sandstone, slate and similar soft or easily broken rock . I lb. 

Limestone and other intermediate rock II-4 lbs. 

Marble, trap, granite and similar hard tough rock. . . .2 lbs. 

While this table serves as a bsais for calculating the amount of explosive 
required to break boulders, it is only approximate, as the weight of the charge 
does not continue to increase according to the number of cubic yards in the 
boulder. Some blasters may prefer the following table, which gives the approxi- 
mate number of sticks required for each diameter of stone. 

17 



Number of IJ4 x8 Inch Sticks of Explosive Required for Mudcapping 
Boulders of Different Sizes 



Sandstone 


slate 


and similar soft, 


Limestone and other 


Marble, granite, trap 


more 


easily 


broken rock 


intermediate rock 


and hard, tough rock 


IHft. 


greatest 


dia. ^4 sticks 


1 3/^ sticks 


2}/^ sticks 


2 " 






" 132 " 


2 


3 


2^ " 






" m " 


23^ " 


33^ •' 


3 " 






•' 2 


2^-3** 


4 


4 " 






•' 4-5 " 


5-7 " 




5 " 






" 7-10 " 







Charges in mudcap blasting may be fired by either 

Firing Charges fuse and caps or by the electric method. The advantages 

of each method are discussed on pages 50 and 55. The 

electric method is the only one that can be used when more than one charge 

is to be fired at the same time. 

The kind and grade of explosives best to use for mudcapping rocks is one 
having a very quick action of great shattering or disruptive power. The best 
explosive for this purpose is one of 40*;;, 50' , or 60', strength. The straight 
nitroglycerin dynamites or powders are a little quicker in 
Kind and Grade action than the "extra" or ammonium nitrate explosives, 
of Explosive and for mudcapping should be the first choice. See page 

44. But the ammonium nitrate dynamites or powders 
are equally powerful, when of equal percentage strength, and though they are 
slower in action, tending to break the rock into larger pieces than nitroglycerin 
explosives, their work is satisfactory for mudcapping. 

When another explosive than those recommended above is on hand on 
account of some other use, it may be used for mudcapping with success, though 
its use may be more expensive. Almost any dynamite or high explosive powder, 
for farm, mine or quarry work, may be used in an emergency. Even the 20 '"^ 
high explosives that are best for soil blasting can be made to break rocks in 
this way, though their performance will not be very satisfactory. When these 
lower percentage explosives are used, particularly if of the ammonium nitrate 
type, the quantity must be increased greatly. The use of such explosives will 
result in cracking the stones into a few large pieces rather than into many 
fragments. Whenever there is much mudcapping to do it will pay to get the 
proper explosive. In cold weather, use only the low freezing grades of these 
explosives. 

The only tools necessary for mudcapping are a shovel, a pocket 
Tools knife and cap crimper, though an old dishpan or similar receptable 
and a water pail often can be used to advantage. 
Breaking average sandstone boulders by blasting by the mudcap method on 
some jobs has cost fifteen to twenty cents per cubic yard. Granite, limestone, 
marble and trap rock boulders have been broken for slightly 
Cost and Time more. Mudcapping costs per cubic yard of rock run up 
fast when the boulders are very large, say larger than 6 to 
8 cubic yards each. Trap and other tough rocks are expensive to mudcap. 
The shape of the rocks has much to do with the cost and practicability of break- 
ing them in this way. 

The approximate cost of mudcapping can be computed on the basis of 
the amount of powder required as given in table on page 1 7. The time required 
to mudcap rocks is very little. When wet ground for the mudcap is at hand, 
a man can have a stone lying round in pieces within 10 or 15 minutes after he 

18 



gets on the ground. Many practiced blasters use no more than 5 minutes for 
each boulder. 

Three feet of fuse burns about a minute and a half and under ordinary 
conditions is enough to permit the firer to reach a place of safety. If an electric 
blasting machine is used, the operator should stand at least 
Suggestions 250 feet away, and should watch for and dodge any flying piece 
of rock coming in his direction. Avoid standing behind a shelter 
that may let stones through, as the branches of a tree. See page 55 for dis- 
cussion of misfires. 

A rock will often break better if it is jacked or pried from the ground and 
allowed to rest on small stones under the ends or corners. Sometimes odd shaped 
rocks, particularly if they are long, are broken better with two or more mudcap 
charges placed at different points and fired simultaneously by the electric 
method, than by one charge. Usually it will be best to locate such charges on 
opposite ends of the rock, though this rule is not good every time. Sometimes 
one may be a mudcap and the other a snakehole or undermine charge. Before 
proceeding with any mudcapping, read the chapter of this bulletin beginning 
on page 43, about the nature of explosives, detonation, tamping, freezing, 
thawing, etc. 

The result to be expected from a successful mudcap blast is to break the 
stone into a great many pieces, none of them too large to handle. If a heavy 
blast is used on a small brittle stone, half or more of the stone may be almost 
powdered, and few or none of the pieces may be much larger than a man's fist. 





Two pictures : How a proper undermine blast can be made to break a stone that is partly buried. Two charges of 
50 per cent, ammonia explosive were used under this stone, and fired simultaneously, with the result shown. 

Undermine or Snaliehole Blasting 

To break a stone by the undermine blast method, the charge of explosive 

is placed against the under side or bottom of the stone with the solid ground 

as its backing. Less explosive is required than with a mudcap. 

Description since the confinement is better, owing to the earth backing and 

the weight of the stone. 

This method is superior to mudcapping because less depends on the shape 

of the stone under the ground or the depth it is buried, which are always hard 

to determine with certainty. 

19 



Undermining or snakeholing works better when the stone to be broken has 
a flat side down, and with flat boulders rather than round ones. 

To shatter a stone by this method, as by other methods, due attention 
must be given to the hardness, toughness and seams. 
Locating the Holes as outhned on pages 17 and 19. 

When a boulder is well buried the first thing to 
do is to probe about it with a sharp quarter-inch steel rod, to learn the shape 
of the under side and the condition of the ground. In any case, the charge of 
explosive should be placed as near as possible underneath the center of weight 
of the rock. 

Holes for the explosive can be made with a crowbar and sledge or with a 

dirt auger. The crowbar likely will be the most serviceable. If the hole is not 

large enough to hold all the explosive required at the right 

Making Holes point, you can make use of a scraper to enlarge the hole at 

the bottom. See page 31 for description. In blasting very 

large rocks, small tunnels can be shoveled out. 

The practice of enlarging the bottom of the hole by "springing" with an 
inch or so of a stick of explosive, is seldom to be recommended in undermine 
blasts of stones, on account of possibly enlarging the cavity too much and 
forming cracks extending into the surrounding earth. 

The explosive should be placed as nearly against the rock as possible. 
When the rock is undermined by digging, the explosive should be packed in a 
compact bulk, as in a mudcap charge. If you get the 
Placing the Charge charge an inch or two away from the rock with dirt 
between, its breaking effect on the rock will be re- 
duced. Read the directions for loading a hole, on page 28, and for placing a 
mudcap charge on a rock, page 16. 

The stick of powder containing the blasting cap should be the last or next 

to the last to go in. The cap should not be against the rock. 

Inserting Cap but if possible in the outside portion of the charge. The 

business end of the cap should be pointing directly toward 

the center of the charge. 

The charge must be thoroughly and tightly tamped. If there is not good 
firm resistance all the way round it will blow the dirt out from under the rock 
without doing any stone breaking at all. It is a good plan sometimes to tamp 
the dirt the whole way round the stone before the charge is exploded. Never 
use a metal tamping rod in the hole or near the charge of explosive. It may 
strike sparks from the rock or from small pieces of stone, and cause a premature 
explosion. 

Firing the charges may be done either by the cap and fuse method or with 
electric blasting caps and blasting machine. Each method has its advantages 
and adaptations to certain conditions as fully explained on pages 50 
Firing and 55. How to prepare charges, including the fixing of the fuse and 
cap, inserting and tying them in the stick of explosive and other de- 
tails, are told on pages 33 and 42. 

The amount of explosive required to shatter rocks by the undermining 

method depends on the size, shape, toughness and hardness of the rock. The 

table here will serve as a guide. These figures 

Amount of Explosive should be high enough for average tough rock, but 

it must be remembered that the amount of explosive 

required does not always change according to the size of the rock to be blasted. 

20 



Approximate Number of Pounds of Explosives Required for Shattering Boulders 
" Snakehole " by Undermine Blasting, per Cubic Yard of Rock, 
Sandstone, slate and similar soft or more easily broken 

rock M lb. 

Limestone and other intermediate rock 1 lb. 

Marble, granite, trap and similar hard, tough rock 13^2 lt)s. 

Some blasters may prefer a table based on the diameter of the stones. 
Such a calculation can be used satisfactorily, but in this case, too, a great deal 
depends on the shape of the boulder. 

Approximate Number of \^i by S inch Sticks of Explosive Required to 
Shatter Boulders of Different Sizes by Undermine Blast 

Limestone 



Sandstone 



}/2 ft. greatest 


dia. 


1 stick 


2 " " 




\H " 


21/2 " " 




^V2 ' 


3 .. .. 




\H " 


4 '« •• 




3-4 " 


5 " 




6-7 ' 



and other 
tough rocks 

13^ sticks 

IM " 

2 

4-6 " 



Marble, granite, trap and 
similar very hard, tough rock 

2 sticks 
3 



If larger sizes are to be broken, 
better calculate the amount of ex- 
plosives required by the cubic 
yard basis. Your figures will be 
more accurate. When rocks are 
to be rolled out without shatter- 
ing, comparatively small charges 
can be used. The following table 
will give an idea of the amount of 
explosive necessary. 

Approximate Quantity of Explosive 

Required to Roll Out Buried 

Boulders 

dia 14 stick 



• ?4 
.1 

.2 




l^ft. 

2H " 

3 " 

4 " 

5 " 
Larger sizes than listed require 

proportionately increased charges. 
The extent to which the 
boulder is buried and the nature 
of the ground also influence the 
amount of explosive required. 

Probably the most economical explosive for breaking rock in this way is 
30% to 50% strength dynamite or powder of either the nitroglycerin or am- 
monium nitrate class. On account of the better confine- 
ment secured in this method, stones can be broken more 
effecti'^ely and successfully with slower and less power- 
ful explosives than by mudcapping. 20% to 40% strength 
21 



A striking illustration of the action of a proper under- 
mine blast. The rock is lifted a few feet and cracked, 
but is not thrown far. Look closely and you can see 
the cracks where they had begun to form at the instant 
the picture was made. 



Kind and Grade 
of Explosive 



explosives often will prove satisfactory. Any standard strength of nitroglyc- 
erin, ammonium nitrate or gelatin dynamite will do the work. 

To roll stones out without breaking them, the high percentage explosives 
can be used successfully, but they are not as well suited to the purpose as the 
slower ones, such as 20' ,' ammonium nitrate dynamite or powder. If you are 
buying explosives for breaking rocks, however, buy those best suited to the 
actual breaking, and do the rolling out of the stones with the same explosive. 

The tools needed in snakehole or undermine blasting of boulders are the 
testing rod or probe already mentioned, a shovel for handling dirt, a crowbar 
or dirt auger, a wood tamping rod V/l inches in diameter, and a cap 
Tools crimper. Several other items in the tool list can be made use of to 
good advantage where there are many stones to undermine. One is a 
3-inch fence post, to tamp the ground tight about the edges of the stone. Another 
is the scraper, for enlarging the bottom of an auger hole. 

Undermine or "snakehole" blasting is a slightly cheaper method than 
mudcapping when conditions are favorable. It is often found that the cost per 
cubic yard increases with stones smaller than one cubic yard, and is very much 
less with stones containing several cubic yards. Sandstone 
Cost and Time has cost ten to fifteen cents per cubic yard to break in this 
way, and the other kinds in proportion. This is one of the 
most serviceable and satisfactory methods of blasting boulders. The cost can 
be calculated by referring to table on page 21. Add labor cost to the total for 
explosives. Sandstone and other such easily broken material can be broken up 
cheaply, while marble and trap come higher. Although the cost of explosives 
is somewhat less than with the mudcap method, this is partly offset by the 
additional labor required in making the holes in the ground. Ordinarily a man 
can make a hole and place a charge under a stone in 1 5 to 20 minutes. 

Combinations of snakeholing and mudcapping sometimes are effective 
with stones that lie on the surface of the ground or are imbedded only a little. 




^^^/ ^TOff/V FUSE 



: FUSE /^/IVHED 
' DANGEROUSLY JAMMED 
"^D/PT BETWEEN STICKS OF POWDER 
^AIRSPACES'.-'':'' . \ ; ' <--4, 



A combination of evils. Such loading could not result in breaking a boulder. Note the seven faults. 

22 



To make use of the advantages of such a combination an elec- 
Suggestions trie blasting machine to produce simultaneous exploding is nec- 
essary. It is not wise to attempt the combination of top and 
under shots when a stone is buried deeply. Better roll it out first. 

Two points of caution are desirable. Beware of misfires. See page 55. 
Remember that snakehole or undermine blasting may throw pieces of rock 
with considerable force and range, but the danger can be reduced 
Cautions to a minimum if proper precautions are taken to see that every 
person and animal is out of range of flying rock and fragments. 
It is not unusual in snakehole or undermine blasting to see pieces of stone 
thrown more than 100 yards. 

Blockholing 

This method of breaking rock with explosives consists in drilling a hole 
into the boulder, putting the explosive at the bottom, tamping tightly, and 
firing in the usual way. It is remarkable how small a charge of explosive will 
break a big boulder, even of the hardest and toughest kind, when placed in 
this way. One stick of explosive in a drill hole 18 or 20 inches deep in a rock 
will do more damage than several sticks on the surface. 

The blockhole method of blasting is the best way of break- 
Description ing large, tough boulders that are not too hard to drill and 
which do not break well from a surface blast. 
Drilling and blasting in a similar way is nearly always the only practicable 
method of blasting ledge rock. 

The nature of the rock has a good deal to do with the point at which it is 
best to place the explosive. Ordinarily it will be found that the charge should 

be located somewhere near the center of the 
Character of Rock and boulder, though different kinds of rock require 
Placing of Explosives different depths of holes. A brittle rock which 

does not split well and a tough rock such as trap, 
must be drilled deep in order to break it right, while a shallow hole will give 
satisfactory results in a rock which is easy to split, or which crumbles apart 
like slate. 

A rule that may be applied to all rock is that the deeper the drill-hole, 
down to 3^ or 3 5 the way through the rock, the less explosive will be required, 
and the greater will be the execution of the blast. In boulders that are very 
hard, and so big that they require a large charge, it once in a while pays to drill 
a very small hole, and then spring this hole at the bottom by exploding at that 
point a small charge of explosive, using no tamping. Such a practice will be 
needed rarely in boulder blasting, though it is often useful in blasting out ledges. 
Holes may be drilled by one man alone, or by two or 
Drilling Facts more men. One-man drilling usually is the cheapest when 
holes are made by hand. The drilling can be done with 
ordinary hand hammer drills, with churn drills (finishing deep holes), or with 
machine drills. 

A hand drill is just a straight piece of drill steel, which is medium hard 
and very tough, with one end shaped into a proper cutting bit. This bit is ^ 
to 3^2 or more wider than the shank of the drill, with the 
Hammer Drills cutting edge somewhat rounded up to the corners and 
sharpened in the form of a "v," the angle of which should 
be long and thin or short and thick, according to the kind of rock to be drilled. 
In soft rock use a long thin cutting edge; in hard rock a short, thick edge. 

23 



You can buy drills of different lengths and diameters from mine supply 
houses or hardware dealers anywhere. Or you can buy the steel from hard- 
ware stores and make them. Drill steel comes in :>8-inch, " s-inch and other 
diameters, in bars up to 20 feet long. If you plan to make your own drills, be 
sure to have on hand a good length of it, for even if you have only a dozen 
boulders to blast you will need several drills as they require sharpening fre- 
quently. 

If one man is to do the drilling, the hand hammer should weigh 3 or 4 
pounds; if two men, 8-pound sledges are about right. All hammers should, of 
course, be flat faced. The drill should be turned about J/g of a revolution at 
each stroke of the hammer so as to keep the hole round. The more regularly 
this is done the nearer true the holes will be and the faster the bit will cut. 
The holes can be started with a short drill — say 8 or 10 inches long — easier than 
with a long drill. 

The right diameter for a hole in a boulder usually will be about one inch. 
It is well to keep the hole as small as possible, for it takes a good deal longer 
to drill a big hole than a small one. For instance, it takes 
Size of Holes about four times as long to drill a 2-inch hole as one an inch 
in diameter. If the 1-inch hole will contain enough explosive 
it should be the size selected. But it must be remembered that as the hole 
goes down, the ears of the drill bit will wear off and the hole will grow smaller, 
so that in hard rock it is well to start a hole that is to go deeper than a foot or 
so, with a drill 3<4 inch larger than is wanted at the bottom. In boulders con- 
taining more than 6 or 8 cubic yards of material it is best to drill inch or inch 
and a quarter holes. 

The holes should be kept wet by pouring in water as the drill goes down. 
In this condition, the drill cuts much faster than in dry holes. It is necessary 
to keep the holes clean. The sledge, as the ground-up rock is called when 
mixed with water, can be taken out with a scraper which is shaped somewhat 
like a very small garden hoe, or with a spoon rod, which is a small wood rod 
with a disc of tin on each end. The discs should be of different sizes, and at 




Pressing in the tamping after a charge of explosive has been seated in the bottom of a blockhole 

24 



one point they should be cut to the center and one of the cut edges bent down, 
so that when the rod is revolved in the bottom of the hole the edge will scoop 
up some of the sludge. 

Another good way of cleaning out holes is to use a spiral hook, or drag 
twist, like an old-fashioned rifle cleaner. Rags or hay can be used on this to 
wipe the hole. A hickory or willow stick with the end split into many small 
pieces, or broomed, is also a good thing for getting dirt out. When this is dipped 
in the sludge, the material sticks to it, and can be lifted out and knocked off 
against the outside of the stone. 

A leather or rubber washer, or some old rags, should be fixed round the 
drill just above the level of the stone, to prevent the sludge and dust from fly- 
ing up into the face of the driller. This is particularly necessary when churn 
drilling. 

A churn drill is a piece of drill steel from 5 to 6 feet long, often having bits 
at both ends. It is used without a hammer — a man raises and drops it into 

the hole. Holes cannot well be started with it. It will cut 
Churn Drills holes faster than a hammer drill under favorable conditions, 

but owing to the way it is worked its use should not be at- 
tempted in holes less than 6 or 8 inches deep. For deep holes and in soft rock 
it certainly should be considered. A good churn drill for 1 -inch holes should 
weigh about 10 pounds. 

Bits should be kept sharp, for dull drills do only a fraction of the work 
they should. To sharpen bits costs about five cents each. It may be done in 
a blacksmith shop or, in emergencies, with a file or on an emery-wheel or grind- 
stone. They should be made as sharp and hard as 
Sharpening Drill Bits they can be used in the rock to be drilled without 
either dulling too fast or chipping. The angle of 
bevel that is best generally will be about 90 degrees for hard rock and 45 to 60 
degrees for soft rock. Your blacksmith will give you the proper kind of bevel 
if you give him the necessary information. Good drill steel is not tool steel. 
Before attempting to sharpen a drill the shape of a new bit should be 
observed. Heat the drills to cherry red, and do not hold them long at that 
temperature. Work to get them hot without delay, then take them out of the 
fire promptly for dressing. 

The bit should be hammered to shape on the anvil, with the shank of the 
drill held so that it has 1 foot rise to 2 feet of length. You likely can use a file 
to advantage to help shape the edge, while the steel is hot. When the bit is 
shaped, it is ready to be put back into the fire and reheated for tempering. 
The tempering should be started when the steel is at a temperature of 430 
degrees F. You can tell the temperature by the shade of the surface or color 

film that forms on the surface as the steel is being heated. 
Tempering Drills When the bit has been heated slowly until the surface 

has nearly a cherry red shade, take it from the fire and 
hold it in the air till it gets a very pale yellow. Rub it on a stone to remove 
the scales so the color can be seen unmistakably. If it seems to take too long 
to reach this color in the air, plunge it into the water and out again at once to 
start the cooling. Then watch the colors by standing in a dark corner. They 
should advance parallel to the edge. If they don't, hold the hot corner or side 
in the water an instant to even up the entire bit. As soon as the very pale 
yellow color is noticed, stick the bit into cool water and leave it there, stirring 
it about till most of the heat has left the steel. 

25 



Temperatures of the steel that are indicated by the colors are as follows: 

Very pale yellow 430 degrees F. 

Straw color 470 

Brown 490 " " 

Purple 530 " " 

Full Blue 560 " " 

Dark Blue 600 " " 

Cherry Red 900 " " 




How a proper blockhole blast will shatter a boulder into pieces of all sizes. Note how completely 
the stone is broken throughout its entire volume and not just at one side or corner. 



The time in which two men with hand drills can make holes in rock can be 
told best by stating the number of minutes it takes per inch of hole in different 
kinds of rock. For beginners, when two men are drilling holes an inch in di- 
ameter in rock such as sandstone, about 1\<2, to 3 minutes per inch in depth is 

required; in limestone 3 to 3J-; minutes; in granite 4 
Time for Drilling minutes; in mica schist 5 minutes; in marble and trap 

rock 6 to 8 minutes. Single hand drilling (one man) 
proceeds about two thirds as fast, except that in soft rock the rate is upwards of 
three-fourths as fast and in very hard rock only half as fast. These figures 
change greatly according to the experience of the workers and the condition of 
the sandstone, limestone, granite, schist, marble or trap rock that is drilled. 

The cost, including sharpening of drills, will run about 25 cents a 
Cost foot in the easily drilled rock up to 70 cents in the very hard, tough 
rock. 
Machine drilling is very much faster than hand drilling, and much cheaper 

where there is enough drilling to do to justify the pur- 
Machine Drilling chase of an outfit. Since there are many owners of large 

acreage which requires clearing, also many contractors in 
stump and stone removing who will use this handbook, some of the data about 
machine drilling will be useful. 

26 



In clear rock, or rock not checked, machine drilling is 5 to 15 times as fast 
as hand drilling. In some sandstone it is possible to go down at the rate of a 
foot in 5 minutes (instead of an inch or two as in hand drilling); and 
Speed in trap rock at the rate of a foot in 10 or 12 minutes. In limestone 
the rate is even faster than in some blue sandstone, there being records 
of instances where a foot has been drilled in 3 minutes. Hard granite and flinty 
rock often drills at the rate of a foot in about 7 minutes. 

Blockhole blasting is more economical than undermining, the cost depend- 
ing partly on how difficult the rock is to drill. Large rocks of a hard 
Cost and tough nature, cost pretty regularly around 16 to 17 cents per cubic 
yard of stone to break by this method. Blockholing requires a smaller 
amount of explosive and larger amount of labor and time than mudcapping or 
"snakeholing." 

The cost of machine drilling usually is much lower than of hand drilling — ■ 
often it is about one-fourth or one-third, of course not including depreciation 
or interest on the cost of the outfit. This is much or little per foot of hole 
drilled, according to how steadily the oufit is used. It may amount to only a 
fraction of a cent, or it may run the total cost up higher than that of hand 
drilling. There are some power machines which it is claimed will drill at a cost of 
6 cents per foot. Others drill at a cost of 10 cents per foot, but 1 cents is high. 




How a boulder can be broken into pieces small enough to handle easily without shattering it into 
fragments, with proper charges of 20 per cent, ammonia explosive placed in a blockhole, or by 40 per 
cent, explosive used as a mudcap. This stone shows by its breaking how joint and bed lines run. 



There are two types of machine drills operated by steam or 

Machines compressed air — the small jack hammer and the large tripod drill. 

The jack hammer drill is the best type of machine for use on 

boulders. Jack drills are portable and easily handled. Tripod drills are heavy. 

The tools needed in blockhole blasting, aside from drills 

Other Tools and hammers, are a pocket knife for cutting fuse or scraping 

wires, a cap crimper and a wood rod for tamping. Crowbars 

are often useful. 

27 



The kinds and grades of explosives that can be used for blockhole blasting 
are many. In fact, rock can be broken by this method with almost any blast- 
ing explosive. But certain facts should be understood by blasters. One is 
that the use of a high strength quick-acting explosive. 
Kinds and Grades such as 50% or 60% powder or dynamite will shatter 
of Explosives rock into small pieces, while the use of slower explosives 

such as 20' , strength will crack and split it into larger 
pieces. Ammonium nitrate dynamites or powders are considered somewhat 
superior to nitroglycerin explosives for this purpose. For the ordinary breaking 
of boulders into pieces small enough to handle easily, there is nothing better 
than 20% to 40% ammonium nitrate powder or dynamite. 

In blasting in quarries, 5 tons of rock often are brought down per one 
pound of explosive. It is difficult to maintain this 
Amount of ratio in the field, unless it be with very large rocks, or 

Explosive Required ledges with an open or free face. Small boulders 
often require more explosives per cubic yard than 
large ones. The shape of the boulder Is also an important point, so the follow- 
ing tables can only be considered as approximate. 

Approximate Number of Pounds of Explosives Required 

to Break Boulders by the Blockhole Method, 

per Cubic Yard of Rock 

Sandstone and other more easily broken rock M It). 

Limestone and other medium rock H It). 

Marble, trap and similar hard, tough rock 3^ lb. 

Figuring on the basis of the diameter of the stones and the number of 
sticks of explosives required, the tabulation is: 

Approximate Number of Sticks of Explosive Required to 
Break Boulders of Different Diameters 

Limestone and Marble, Granite, Trap, 
other medium and similar hard, 

rock tough rocks 



Sandstone, 


Slate and 


similar easily broken 




rock 


\y>h. 


dia. 


34 sticl 


2 " 




H ' 


2K2 ' 




Vz ' 


3 ' 




H ' 


4 ' 




1 


5 ' 




13/2 ' 


7 ' 




6 



K2 
M 

2 



stick 



stick 



Often from experience, an observant man will learn just how much ex- 
plosive is required to crack a stone and lay it apart without excessive throwing 
of pieces, danger and waste of explosives. 

All water should be wiped out of the holes. If the holes are smaller than 
the sticks of explosive the paper wrapping of the sticks will have to be removed 
and the explosive pressed into the hole so that there are 
Loading Charges no air spaces. The cap should be placed in the charge 
near the top. Tamping of damp or wet clay or other 
earth should be placed solidly over the explosive to the mouth of the hole. 
Results of the blast with the smallest charges will be poor unless there is at 
least 6 or 7 Inches over the powder. 

28 








An undermine blast that was too heavy was used here to break a very hard, tough boulder As 
a consequence the rock is broken only into large pieces and these are thrown long distances. A better 
way would have been to have used a very heavy mudcap blast on top of the rock, or. stiU better, a 
proper oiocKnole blast. 



The firing of blockhole charges may be done either with fuse and cap or 

by the electric method. If more than one charge is to be fired, the 

Firing electric method will enable you to put them all off at once. Electric 

firmg is of much advantage in blasting out ledges, and also in firing 

the very small charges sometimes used to break stone to certain dimensions. 

Sometimes what may be called a " semi-mudcap " blast can be used in 

very hard stone, or in stones that are difficult to drill. Drill a hole into the 

stone for 3 to 8 inches, fill with explosive, let the rest of the charge of explosive 

pile up on top of the rock as you would a mudcap charge, in a low cone with 

steep edges. Cover this with 6 inches or more of wet clay. 

Boulders that are buried may be thrown out of the ground before they 

are blockhole blasted. When the earth is supporting them on 

Suggestions all sides they may not break quite as well. Digging round 

them or raising them off the ground with a jack or pry. and 

letting them rest on small stones placed under the ends or corners, helps to 

break them up better. 

Blasting in drilled holes is practically the only method that is effective in 
breaking up ledges of rock, either underground or above the surface. Drill a 
line of holes along back of the edge or face of the ledge 
Breaking Ledges above the surface. It is not necessary to dig or blast 
away the dirt from a ledge. The quantity of explosive 
required can be gauged by the table giving the amount to use per cubic yard 
of rock. Use half again as much explosive in a ledge blast as in a boulder. 
Measure the distance from the open side or face of the ledge back to the drill 
holes, and compute the number of cubic yards that should be broken off. 

Ordinarily on farms or in roads it is desirable to break up ledges to a depth 
of about 2 feet below the surface. To do this the holes should be put down 
slightly more than 2 feet and should be located 2 or 3 feet back from the face 
of the ledge. To break ledges deeper, drill deeper holes farther back from the 

29 



face and charge heavier. The deeper holes can also be farther apart. Two- 
foot holes usually can be 5 feet apart in soft, brittle shale and slate. 4 feet apart 
in limestone, and 3 feet apart in harder material. The spacing between the holes 
should be about the same as their distance back from the face. The details of 
charging holes, drilling, tamping, firing, etc.. that have been giving for boulder 
blasting apply equally to ledge blasting. 

Blockhole blasting is perhaps the most efficient method of breaking rock 
that is known, and from it you can expect perfect results. If you use a proper 

charge of a quick explosive, the rock will be shattered 
Results to Expect into small pieces. If you use a slow explosive, the rock 

will be broken into larger pieces. In any case, the use 
of the charges recommended here will result in the satisfactory breaking up of 
any rocks you may have to deal with. 




How boulders are shattered into fine pieces by heavy mudcap charges of 60 per cent, nitroglycerin 
explosive. Note the amount of stone that is so small it will not need to be hauled away. 



General Considerations 

The information on boulder blasting, and particularly on the breaking of 

ledges of rock, applies to quarrying limestone or road material, gravel, etc. 

In quarrying. It Is better to drill larger holes than one inch. 

Quarrying Proper loading In Inch and a half holes, drilled to depths of 6 or 

8 feet, and 5 or 6 feet back from the edge of the quarry ledge will 

loosen large quantities of rock. 

It does not pay to dig hard-set gravel or sand by hand, for in such material 
the holes are easy to drill, and comparatively small charges of explosive will 
loosen great quantities. For quarrying use 40' ,' ammonium nitrate explosive 
unless the rock is wanted in large pieces, when 20' ;. ammonium nitrate grades 
will be better. For the semi-rock, hard gravel, etc., use 20'; explosive, the 
granular powder known on the market as R.R.P., or if the work is dry, black 
blasting powder. Medium tough rock can be quarried at a cost of 50 cents per 
cubic yard. Including the cost of drilling but not of crushing, screening and 
hauling away the stone. 

30 



Emphasis should be placed on the possibility of using explosives as a labor 
substitute. To illustrate, take the disposal of a 4-foot sandstone boulder. To 
drill this with an inch hole 32 inches deep would require about ]}/2 hours, or 
slightly lesS; for two men. But one man can smash the same boulder within 
10 minutes by placing a proper mudcap blast. In the 
Explosives as a first case the breaking of the boulder is achieved with 
Labor Substitute greatest economy in total outlay, but in the latter case 
it is broken by one man, and broken without interfering 
seriously with other work. On many farms there is so much to do and men are 
so scarce that to take the \} o hours for the boulder's removal is out of the 
question, and the boulder remains in the field — unless it can be broken up with 
little labor and loss of time. 

When a boulder that is nearly all buried is rolled out and blasted, there 

likely will be room in the hole for many of the large pieces, deep enough to put 

them all below the plow line, but it is not well to bury 

Disposal of Pieces pieces larger than 6 inches in diameter, as the broken 

rock will be valuable for building purposes, for road 

making, lining ditches, etc., and should be kept in the stone pile until needed. 

It costs about 35 cents a cubic yard to haul pieces of stone away, figuring 

on the average haul. Solid rock of average density weighs about 2 tons to the 

cubic yard and loose material as it falls weighs about 1 ^ 3 tons to the cubic 

yard. It is better to put a stone rack on a wagon if a wagon is used. 

Hauling Such a rack can be made of 2 or 3 inch plank. To get heavy pieces 

of stone on the wagon, use planks to skid or roll them up. If the 

pieces are very heavy, use a "stoneboat " instead of a wagon. It is better for 

short hauls because it saves so much lifting. An average load of stone is about 

a ton and a half, and two men will handle this in about half an hour, including 

loading and unloading. 

The holes from which boulders have been taken should be filled level, to 
avoid a low place in which water will gather during wet weather. To fill the 
depressions, a horse drag scoop such as is used in excavating 
Filling Holes dirt is a useful thing. If this is not available, a good thing to 
use is an ordinary road drag, or a split log. By standing on 
the drag or log it can be made to gather a lot of ground, and the dumping can 
be done by taking off or shifting your weight. 

In addition to various tools described under the separate headings on 
methods, blasters of boulders will find a heavy crowbar and an iron wedge to 
be useful at times for prying apart pieces of rock. Some blasts will be found 

steel bar for making 
boles. 



SoU auger — note 
long point. 



not quite heavy enough to throw the stones apart. 
Tools and Appliances though they will crack the rocks through and 

through. These stones can be reduced with a sledge, 
but a little prying will accomplish more than a whole lot of hard hammering. 
If the bar cannot be forced into the crack use the wedge and sledge it in. Be 
careful that the wedge does not strike solid rock at a bed or joint line running 
at right angles. The wedge should be a slim piece of tough steel, 6 inches long 
and an inch or two thick at the base. 

31 



The best tamping material is damp clay. Tamp the hole full, while working 
in the tamping with the stick in one hand, hold the fuse or the electric wires 
out of the way with the other hand. It is easy to damage fuse 
Tamping and wires by breaking the insulating with a pebble, or with the 
edge of the tamping rod. It is also easy to pull the cap out of the 
primer charge unless the fuse or wires are held firmly against the rock. Many 
misfires are due to carelessness at this point. 

In lighting a fuse, stick the flaring head of a burning match right against 
the powder in the end. See page 4 1 . This will work in any wind. The fuse 
always gives a pronounced spit as soon as it is lighted. Do not leave before the 
sparks and smoke begin to spit out regularly. 

It may be safe to stand 100 to 150 yards away from a blast that is not 
overloaded, but this is a matter which each blaster will have to decide for 
himself. So much depends on the proportion of the charge to the boulder, its 
location, and as to whether the stone is solid. The right 
Flying Pieces charge will not throw stone far, but a charge that is too 
heavy, or in the wrong place, will throw large pieces for long 
distances. In fact, this is one of the ways in which you can tell whether or not 
you are using too much explosive. In any case, to be safe, keep an eye on the 
blast and dodge any flying fragments coming your way. 

Use every care to keep everybody beyond the range of danger. The man 
who fires the charge should keep his eyes open for stones coming down several 
seconds after the blast and at distances 100 yards or farther away. 

They are dangerous. See page 55 for discussion of 
Watch Misfires their cause and remedy. 




How a large granite sandstone or limestone boulder can be shattered with a mudcap blast. At 
the point next the explosive the stone is broken into small fragments, but at the other side it is left 
in large pieces, though it is well cracked in every direction. 



32 



Preparing Charges of Explosives for Firing 

A charge of explosives for the purposes of these directions is considered to 
be all the explosives needed for a single hole with cap and fuse or electric 
blasting cap properly inserted in the stick of dynamite or 
powder (see pages 36 to 37) and tamped in the hole, ready 
What a Charge is to fire. The preparation of charges is practically the 
same for all sorts of farm blasting. The slight varia- 
tions advisable to suit different kinds of work are not 
enough to call for separate treatment, since the principles are all the same. 

All who use and buy explosives should read the next chapter, beginning 
on page 43, on the nature and actions of explosives. It is only the man who 
understands all the facts mentioned there who will be able to load and blast 
with greatest ease, speed and results. 

Scope of This Chapter 

It is important for everyone who blasts to understand why he does things, 
as well as how to do them. For that reason the following discussion of the 
preparation of charges is made full and complete, with due attention to all 
the important factors involved. Details of any particular part of the operation 
can be found quickly by referring to the heading desired, as given in the index. 

Readers who may not desire a full discussion are referred to the following 
brief outline of the process. 

Be careful that explosives, cap and fuse are in perfect condition. Cut a 
length of fuse sufficient for the hole to be loaded, making the cut clean, with- 
out dragging ends, at a slight slant of, say, 30 to 45 degrees from right angle. 

Pick a cap from the little tin cap box, carefully, with your fingers, and 
slide it gently on the end of the fuse. With a proper cap crimper fasten the 
cap securely to the fuse, making the crimp close to the open end of cap. Avoid 
twisting or punching the end of fuse against the bottom of cap as well as draw- 
mg it away from the bottom. For wet work waterproof the joint of cap and 
fuse with tallow, soap or other material. Do not use thin grease or oil. 

Next punch a hole at a long slant in the side of the stick to be primed. 
Better use a wooden punch for the purpose. The handle of the cap crimper 
may be used. 

Insert the cap in the hole made as described, tie the fuse in place, and, 
for wet work, waterproof all openings in the stick. You then are ready to load. 

Provide space enough in the hole at the proper point to hold the required 
amount of explosives in a bulk that is not too long. Be sure before you start 
to press in the sticks to the bottom of the hole (see page 28) that there is 
enough clearance to permit their easy and certain entrance. Tamp fully and 
firmly up to the top of the hole. 

The charge is now ready to fire, which may be done by pressing the burn- 
ing or flaring head of a freshly scratched match against the powder in the split 
end of the fuse. 

Carrying Explosives and Supplies 

The place to keep the explosives is in the magazine or storage place, and 

not with you in the field. Carry with you in warm weather only enough for the 

job or the day, or in cold weather only as much as can be 

Protection ^^P\ warm and in condition for firing until you are through 

of Explosives '°^<^'"g' ^^^P explosives separate from caps. 

^ A good way to carry the caps, fuse and small tools is 

in a basket. Put a piece of blanket in the bottom, to keep 
33 



out dampness when the basket is on the ground. Some blasters use an 
explosives box for the purpose, putting a wood handle or double wire bale on 
it. The tight wood box probably is a little better than the basket because it 
affords somewhat more complete protection to the contents. 

Whatever the method of carrying the explosives, it should be well pro- 
tected. This consists in keeping the hot sun off it, keeping rain and fog off 
it, keeping it away from dampness of the ground, and keeping it safe from 
meddlesome people and animals. 

Many blasters prepare charges before going to the field, but it is better 
practice to carry along the tools and materials, and to put them together or 
make the primers on the spot after all the holes are made in the ground or 
rock, and when everything is ready for the firing except to put the explosive in 
place. 

These remarks are given as reminders. Full discussion of proper handling 
and storing of explosives can be found on pages 58 to 60 respectively. 

Tools and Materials Required 

The first step in preparation of charges is to assemble the following: as 
many sticks of explosive (or parts of 
stick, if charges are to be less than full 
sticks) as there are holes to be primed; 
an equal number of caps; a sufficient 
quantity of fuse; some string; a wood 
punch with an end the size of a cap for 
about 3 inches; a pair of cap crimpers; 
a pocket knife. If the holes are very 
damp or full of water you also will need 
some tallow or other waterproofing 
material. In certain cases a sharp 
hatchet or axe and a block of wood will 
be worth having. The purpose and use 
of these items will be made clear later. 




A handy box for carrying supplies to field. 



Putting Caps and Fuse Together {Making Primers) 

Fuse is described as to sizes and properties on page 57 and caps on 
pages 56 and 57. Readers who are not familiar with them should turn to 
those pages at this point. Unroll the fuse and cut off a length that will be 
enough, since fuse burns about 2 feet in a minute (there are variations — see 
page 58). 

Three feet will give you 13^2 minutes or a sufficient time to get beyond 

danger under ordinary conditions. The fuse, of course, must 

be long enough to reach out of the mouth of the hole when the 

The Fuse charge is in place. Measure the depth of the hole before you 

cut the fuse. 

Warm cold fuse before attempting to bend it. It may be 
taken into any warm room for the purpose but should be subjected to no heat 
greater than 1 10 degrees. If for any reason you have doubts about the con- 
dition of your fuse, cut off a foot or more and try it without any cap or explo- 
sive. If it will burn properly it is all right. 

Be sure to get fresh ends both for the match and to put into the cap. If 
fuse has been cut for some time into lengths, it is well to cut off short pieces 
from the old ends in order to bring fresh powder right to the tips. 

34 



Cutting the Fuse 



Cut the fuse off at a very slight angle or bevel — say 30 to 45 degrees, as 

shown in the diagram. This slant is for the purpose of giving a little space 

between the actual end of the powder and the explosive 

material in the bottom of the cap, to enable the spark 

to spit into material. 

The only way to regulate the space is to cut the 

fuse as directed and let the long tip rest gently against 

the bottom of the cap. The spark has a better chance to ignite the explosive 

material in the cap when it spits from the end of the fuse than when it merely 

burns up to the end without any space to spit into. 

The end of the fuse where cut off should be clean and free from dragging 
ends and threads. If it is not cut off clean, part of the covering may double 
over the end of the fuse in the cap and keep the spark away from the explosive, 
causing a misfire. Be careful to keep both ends of fuse off damp ground and 
out of puddles of water. 

If the fuse has been mashed, or is too thick to go into the cap easily, do 
not peel off any of the covering. Reduce the diameter by squeezing it with 
the cap crimpers or by rolling it on a smooth surface under a knife blade or 
other smooth implement. Sometimes you can reduce it by rolling it between 
the thumb and finger. 

The very best way to cut fuse is on a block of wood with a sharp knife. 
The blade can be pressed right through the fuse and will make a clean cut. 
Another good tool is a sharp axe, to be used on a block of wood. The method 
of cutting is of small importance, just so the actual cut is made smooth and 
even enough. If you do use other tools, have a knife with you to trim up ends 
that are not true. Be careful to avoid twisting, pinching or otherwise knock- 
ing the freshly cut end of the fuse about, for you may shake out the powder 
back far enough to cause a misfire. The powder should come out flush with end. 
To get one cap out of the tin box in which they came, tilt the box up on 
edge till some of the caps slide forward, and then pick the cap up with your 
fingers. Don't attempt, on penalty of losing a hand, to take a cap out of a 
box by running a nail or a little stick or the fuse into it in the box. Be care- 
ful you do not drop a cap to the ground or floor. 

Turn the cap upside down, to make sure there is no dirt in 
it, and gently slide it on the fuse till the end of the fuse just 
touches the bottom of the cap. Do not ram, press or twist the 
end against the bottom. 

Hold the fuse with capped end up, to keep the cap from 
sliding off, and crimp the cap fast. This you do with the special plier-like 

tool called a cap crimper. The 
"crimp" is made by pinching the 
open end of the cap 
tight to the fuse. It 
Crimping should be made with- 
in the last quarter 
inch of the open end 
of the cap. Never make it toward 
the closed end because you might 
disturb the explosive material in 
the bottom of the cap and cause it 

"Crimp" or fasten caps to fuse with a regular crimp- {._ ^vrkln<-l<a 
ing tool. This tool does the job far better than it *■" cxpiouc. ^ 
can be done in any other way. Cap crimpers are supplied by 

35 



The Cap 




all makers of explosives. Order one or more when you buy your explosive. It 
is well to have an extra one about to use in case you lose one on extensive jobs. 
This fastening of the fuse to the cap is one of the points in blasting where 
a great deal of abuse occurs. Blasters think they can take a chance with danger 
or with misfires, and attempt to crimp the caps some other way. Except in 
extreme emergency don't try to crimp a cap with anything except a regular crimp- 
ing tool; but there are times when one may not have a crimper nor be in a posi- 
tion to wait till one can be purchased. There is a way out of this difficulty 
— which is to secure a makeshift crimp with something else than a crimper. 
It is possible to use a pair of pliers, or a small pair of pincers, and accomplish 
something that may hold the cap on the fuse. The best makeshift crimp is 
to take a fold of the cap up at one side of the mouth with a pair of close 
fitting, square-nosed pliers. Be careful while doing this that you do not 
grind the end of fuse against the bottom of cap, or pull the end back from 
the bottom. If the fuse should pull away from the bottom of cap a quarter 
inch, a misfire likely would result. 




Waterproofed (tallowed) sticks ready for loading in wet holes. 



When the charge is to be placed in a dry hole, waterproofing is not needed, 
but in a wet hole the connections between fuse and cap 
must be made water-tight with tallow or soap. Do not use 
Waterproofing grease, because it may unite with the tar in the compo- 
sition of the fuse cover and soften it, when the powder train 
will be ruined. Water in the cap will surely make it worthless. 

Inserting Caps in Explosive 

The best location for a cap in a stick of explosive for farm blasting is in a 
hole in the side, about an inch and a half from one end. The best position 
for the cap at this point is at a slant that takes it in from the side toward the 
center, but as near longways, or parallel with the sides of the stick, as possible. 

36 




In cutting fuse from roll Takiog one cap caiefully Inserting fresh end o{ 

use sharp knife. from box. fuse in cap. 




Crimping cap with the 
cap crimper. 



Fuse tied firmly to stick 
with string. 



Electric Blasting— Pass the 
doubled fuze wires through 
a hole in stick of powder. 




Loop the doubled end of 
fuze wires over end of 
stick. 



Pull loop tight, bend wires 
at cap, punch slanting hole 
in stick high up and round 
to side a little. 

37 



Insert cap in slanting hole 
to bend of wires, take up 
slack in wires. (Waterproof 
holes if ground is wet.) 



In other words, when making the hole for 

Position of the cap in the explosive, make it with as 

Cap in Stick long a slant down toward the other end of 

the stick as possible. There are reasons for 

this connected with superior or inferior detonation. 

Another style of priming much used is to set the cap 
in a hole made in the end of the stick of explosive, and 
then to tie the paper about the fuse or wires. This is good 
so long as it is not damaged, but experience shows that the 
tamping stick often bends the fuse over sharply when the 
primed stick is pressed into the hole and sometimes even 
interferes with the cap itself. With side priming there is 
a cushion of the soft explosive between the end of the stick 
and cap. End priming always is good provided sufficient 
care is taken in loading to prevent disturbing or displac- 
ing the fuse or cap with tamping rod. 

When all the explosive is removed from its stick 
wrappings, the cap must be inserted in the loose explo- 
sive. This should be done by making a hole, as in a stick. 



pays to take all the explosive out of stick wrappings, 
leave a half stick of explosive intact for the cap. 



Bad priming. 

But it seldom 
Nearly always you can 




A good crimp. 

To make the hole for the cap use the handle of the cap crimper or a 

wooden punch just a little larger than the cap. The hole should be large enough 

to let the cap in without much pressing, but should leave no 

air space about the cap. The depth of the hole also is im- 

Making Hole portant. It should be just enough so that the entire cap 

in Explosive can be buried in the explosive, but not any deeper. If it is 

deeper, the cap may be forced on down to the bottom, which 

will leave some of the fuse in contact with the explosive 

(may cause burning instead of exploding of powder), or the cap may be seated 

just inside the wrapping, leaving an air space at the inside end or bottom of 

the hole, which may lower the effectiveness of the explosive. 

When the cap is seated in its hole in the side of the stick, the fuse will 

extend up along the stick past the near end. It must be tied in this position, 

so securely that the fuse and the cap will not be pulled 

back in handling or by rubbing against the side of the hole 

Fastening Fuse when the stick is pressed down. The best way to secure 

to Explosive it is to wrap a strong string several times below the point 

where the cap is inserted, then give two or three wraps 

about the fuse, and pull tight and tie; or take two loops 

about the fuse and then several wraps about the stick. 




Cutting stick in two — roll It under knife blade. 
38 



When the foregoing directions have been complied with you have a stick 
of explosive primed with a cap and fuse. It is ready to put in the hole in the 
rock or ground. 

Loading Charges in Holes 

You will need a tamping stick. This must be of wood, and had better be 
about the size of a stick of explosive, which usually will be 13^ inches in diam- 
eter, except in case of blockhole blasting of boulders, when a smaller stick 
sometimes is needed to go in small drill holes. Never use a metal rod for 
tamping. Make sure that the hole is ready. It must be big enough to allow 
sticks of explosive to slide down easily (except in the case of small holes drilled 
in rock, when the explosive all must be taken out of the 
Tamping rod stick wrappings and crumbled and pressed into the hole). 
Loose stones, sharp stones and roots that obstruct the hole 
should be removed with a bar or spoon scraper. This work must be com- 
pleted before starting to load. If obstructions fall into the hole, after some 
of the explosive is in place, don't try to remove it by force. Make another 
hole at a safe distance from the first, put in another charge and fire it. 

Measure the hole with your tamping stick and judge if there is space for 
the required charge at the right point. Nearly always a charge of explosives 



aS 



The tamping rod should be of wood. 

should be as much on a pile as possible. If one or 2 sticks are all the explosive 

required, it usually will not hurt to 
put them end to end. But if 3 or more 
sticks are required, to put them end to 
end makes the charge too long, and 
places the force of the blast elsewhere 
than where it should be. 

When your judgment tells you 
that the charge should be in a more or 
less round bulk, enlarge the hole at the 
point where the charge should be made. 
Sometimes this can be done by scrap- 
ing it out at the bottom with a toe-bar 
or spoon-bar. Again, if much enlarg- 
ing is required, it is well to use a small 
amount of explosive to secure it. This 
is called springing. To do this prime 
about a quarter of a stick as usual, 
and push it to the bottom of the hole. 
Use no tamping. After it is fired wait 
till the hole cools, and you will find 
a cavity large enough for your full 
charge. 

It is better to avoid springing 
holes if you can, on account of the fact 
that the cavity often is enlarged too 

much, and the surrounding earth is loosened so much as to injure confinement. 

(See page 47 on detonation). A great deal can be done by scraping the small 

auger hole out to 2 or 3 inches in diameter at the bottom and then causing the 

39 




Slitting the paper wrapping of stick to let it 
swell to fill dry hole. 



sticks to enlarge and fill the hole solidly. To accomplish this enlargement of 
sticks, slit their wrappings 3 or 4 places lengthwise, from end to end. Then 
press them home with the tamping stick. They will expand and shorten. Four 
to 6 sticks in this way can be got into the full length of two. 

Still another way is to take the explosive entirely out of the stick 
wrappings, and with the help of a tin or paper tube, such, for instance, as 
calendars are mailed in, funnel it down to the bottom of the hole. But neither 
this method nor slitting the sticks is wise in wet holes. It is true that 
nitroglycerin powders will stand considerable water, but the safe rule in wet 
blasting is to leave the sticks intact. Ammonia powders or dynamites will 
not stand wetting inside the paper of the sticks without damage. (Never 
under any circumstances cut, break, unwrap or punch holes in explosive that 
is frozen. You invite an explosion in your hands when you do). 

When there is more than one stick in the charge, place the primed 
stick on top of the others — put it in the hole last or next to last — when 
using the cap-and-fuse method of firing. 

Be sure that all parts of the charge are in firm contact. It will not do to 
have air spaces, or dirt, or wrinkled paper between the sticks. While all the 
powder likely would go off under these conditions, it will not do as much 
work as it should. 

The sticks of explosive may fit tightly in the holes. In that case do not 
ram or pound them, but press firmly against them, one at a time, with the 
tamping stick. Press the explosive into tight contact with the sides all round, 
at the bottom of the hole. 

Tamping 

Tamping is a necessity. The charge should be tightly confined. It is only 
in springing holes and sometimes in digging post holes that no 
tamping is advisable, and in ditching that the quantity needed is 
Tamping less. 

When the explosive is in place at the bottom of the hole, 
start the tamping by rolling in some loose ground. Keep the 
tamping stick working up and down to seat this ground against the explosive, 
though make no effort to get it tight till there is a few inches or so over the 
explosive. An exception to this rule is in the case of blockhole blasting of boul- 
ders and ledges, when damp clay tamping should be packed solid all 
the way down to the explosives. The rule for the least contents of tamping 
that will do good work is that it should be 6 or 7 times as deep as the hole meas- 
ures in diameter. 

If the tamping is less than this, the best results will not be secured, 
hence deep holes often are necessary for the sake of confinement of charge as 
well as to contain the amount of powder used. 

Hold the fuse to one side with one hand while the tamping stick is worked 
with the other hand. Rake the dirt to the mouth of the hole and be careful to 
get in the hole only earth — not clods, sticks, grass, etc. Be very careful not 
to damage the cover of the fuse with the tamping stick. 

Fill the hole to the top with tamping, and make it tight. The best material 
for tamping is moist clay. Tamping material always is better when made wet 
enough to ball. In fact, there isn't much better tamping than water itself in 
the hole, when it can be made to cover the charges deeply enough. Use the 
heaviest earth within reach, and if it is dry, better carry some water for 
wetting it. 

40 



Firing 

The free end of the fuse will stick out of the hole filled with tamping, 
say about 4 inches. Your remaining work is to set fire to the powder in the 
fuse, till it begins to spit continuously. Split the end of fuse with your 
pocket knife to make it light easily. Put the flaring head of a freshly 
scratched match against the powder exposed by the cut. (See page 50.) 

Preparing Charges for Electric Firing {Making Primers) 

Up to this point in the directions for preparing charges the text has spoken 
only of caps and fuse. When the firing is to be done with an electric blasting 
machine instead of fuse, you must use electric blasting caps. 

These come from the makers with the wires already fastened in them. 
(See pages 56 and 57.) They are ready to be inserted in the stick of explosive 
without any preparation such as ordinary caps and fuse require. 

Make a slanting hole in the stick of explosive just as is described on pages 
36 to 38. Into this insert the electric blasting cap, letting its wires project 
just as the fuse does when fuse is used. Then tie the wires to the stick with a 
string as fuse is tied, to prevent the cap from being pulled partly or entirely 
out of the hole. 



/ 






Bad method of fastening wires. Bad position A cap in stick, and of cap wires. 

It is better to tie them. 

It is a little difficult to tie the wires tight enough with a string to prevent 
slipping. Another way to fasten them securely is to pass the wires through 
the stick. To do it punch a hole straight through the stick of explosive about 
the middle. Double the wires about 6 inches back of the cap and pass the 
doubled end through this hole. Then loop the doubled ends from the other 
side back round the lower end of the stick. Take up the slack in the wires 
and you will have a sure fastening. The cap can be inserted in the stick at 
another point, in a slanting hole, just as described previously. 

In fixing wires of electric blasting caps to sticks, avoid crossing them and 
avoid bending them sharply or in any manner that will break their insulating. 
If the insulating is broken it likely will cause a short circuit, which will result 
in a misfire. Never take a half hitch about the stick lOith the wires. Do not pull 
at the wires and the cap, because to do so may break the fine bridge wire that 
causes the cap to explode when the current goes through. 

Load these primed sticks the same as is directed for fuse primed charges. 
Be careful to avoid rupturing the insulating on the wires with small stones in 
the hole or with the tamping rod. 

41 



The finishing of the tamping leaves two wires projecting from each hole. 
They must be connected with the blasting machine or other source of current 
with connecting wire and leading wire, in the manner described fully on pages 
51 to 53. Further discussion is not needed at this point. 

Some General Suggestions 

In priming sticks of explosive with fuse and blasting cap, you must be 
careful to avoid permitting the fuse to touch the explosive. High explosives 
will burn like gasoline or coal-oil. They are very easily set on fire by sparks 
spitting from fuse. When they are burning the explosion will be very much 
weaker than it otherwise would be, and will give off noxious gases. 

A very frequent cause of misfires is the bending, kinking and crooking of 
fuse. This is especially frequent when the cap is inserted in the center of the 
end of the stick of explosive and then carelessly forced over against the side of 
the hole by the tamping stick and tamping material. Keep the fuse straight, 
and never under any circumstances lace it through the stick of explosive. That 
is a sure cause of trouble. 

If it becomes necessary to remove a cap from a primed stick of explosive, 
do it gently and carefully, and unless the cap and fuse are immediately to be 
inserted in another stick, destroy them both by lifting a shovelful of earth 
and putting the cap under the ground in the hole, after which light the fuse 
and go away. 

It is better not to lift or carry the primed stick of explosive by the fuse 
or wires when it can be helped. When a practice of carrying primed sticks 
by the fuse is made, misfires and poor explosions will be caused, not every 
time, but often enough to make it wiser not to do so. The cap often is pulled 
back in spite of the tie string. 

Where explosives that are subject to water damage are used in work that 
is wet, matters can be helped by making the sticks waterproof with tallow, 
paraffine or other suitable material. It is practicable to stop all the seams on 
the sticks, load and fire without delay, even with explosives that would be 
put out of business if the water got at the actual material instead of only at 
the wrappings of the sticks. Pay particular attention to waxing or tallowing 
the place where the cap and wires go into the stick. 

When doing wet blasting, use every care to keep the outer end of the fuse 
from dropping into the water or from resting on damp ground. The inner 
wrappings of fuse and the powder train itself take up water like a blotter. On 
a very foggy day it is well to keep fuse in a closed box. Mist and rain, of 
course, will damage it. 



42 



Explosives and Blasting Supplies 

The catalogs of manufacturers are not intended to give all the fundamental 
facts about and the differences between the various explosives. To do so 
would take too much space. They give the trade names and the measure- 
ments and weights of sticks and boxes, demanded by purchasers, and are pre- 
pared on the supposition that blasters and buyers of explosives know what 
they need. This bulletin includes explanations of the names under which 
blasting explosives are made and marketed, outlines their properties, and makes 
clear the work and conditions for which each grade is intended and suited. 

Explosices 
There are scores of different kinds of explosives made and used for blast- 
ing purposes, and many dozens of different names used for them. The most 
familiar name of any explosive in America is dynamite. Another 
familiar term is powder. Other names are farm powder, quarry 
Names powder, contractor's powder, coal powder, stumping powder, Jud- 
son powder, gelatin, blasting gelatin, R. R. P., giant powder, blast- 
ing powder and dozens of others. 
Nearly every one of the explosives designated by these names are made 
in several strengths, and in qualities to suit varying conditions. For this rea- 
son figures and other marks are attached to the names to distinguish the grades. 
In addition to this some of the names are used to designate not only one cer- 
tain explosive but several widely different ones. This is particularly true of 
the names dynamite and powder. The selection of names in the preceding 
paragraph is made for illustrative purposes, and is not to be taken in any sense 
as a recommendation of those explosives for any purpose. The recommen- 
dations are given in detail on other pages. 

All blasting explosives are not made from the same ingredients, and they 
differ a great deal in many other ways than in quality, as quality is generally 
understood. You can buy cornmeal that is good, bad or indifferent, but when 
you buy explosives you will find there are few which can be 
classed as of poor quality. Nearly every standard kind and 
Differences grade is of excellent quality for some particular purpose and 
condition. And practically every one can be classed as of poor 
quality for conditions and purposes to which it is not suited. 
Nor is the difference one of size of stick or grain, as the case may be, though 
this is one element. The main differences are ones of strength, quickness or 
speed of gases, sensitiveness, resistance to cold and to water, density, fumes 
and cost. Some explosives are suitable for wet work, and others only for dry 
work; some are adapted to blasting hard, tough rock, others to blasting ground 
only; some freeze when chilled a little; others can be exposed freely without 
freezing. And it should be noted that many of the better explosives of to-day 
have been developed during recent years and are comparatively new. The ex- 
plosive to buy for any particular work is the best one on the market for all 
the conditions involved. 

Black blasting powder has been known and used for several hundred 
years, and it is practically the same to-day as it has been for a long time. It 
is composed of saltpeter or nitrate of soda, sulphur and char- 
coal. It does not vary in strength, and varies little in other 
Explosive properties. 

Ingredients The dynamites and high explosive powders have little or 

no relation to black blasting powder. They depend for their 
explosive force on other explosive chemicals the best known of 
43 



which are nitroglycerin and ammonium nitrate. It is not necessary in this 
brief description to name additional explosive elements. 

The first dynamite was made in Europe by mixing nitroglycerin with a 
light spongy earth, and packing the mixture in paper tubes as sticks of dyna- 
mite and powder are packed to-day. Nitroglycerin itself is a wonderfully ef- 
ficient explosive when it can be controlled, but it is so dangerous and unstable 
that it must be mixed and treated to make it safe enough to handle. 

As other explosive chemicals become better understood, it has been found 
of advantage to substitute materials that are explosive for the light earth used 
to absorb the nitroglycerin. And more than that, the nitroglycerin itself has 
been displaced to varying degrees in some of the powders and dynamites by 
ammonium nitrate and other materials. Few blasting explosives contain no 
nitroglycerin at all, but many contain only 4 or 5 per cent, of it. Each of these 
combinations of materials, or formula, has its own peculiarities in addition to 
variation in strength, all of which information it is well for a buyer and blaster 
to understand. 

The explosives marketed as "straight dynamites" and "straight powders" 
are made from nitroglycerin. Those made from an ammonium nitrate base 
are called by many manufacturers "extra" dynamites and powders. Gelatin 
dynamites and blasting gelatin are nitroglycerin explosives in which the nitro- 
glycerin has been combined with gun cotton. The various special mine, quarry, 
stumping, farm and other miscellaneous dynamites and high explosive powders 
on the market are not so named that their ingredients can be determined with- 
out a statement from their makers. 

The power of an explosive and its violence are two different qualities. 

The power, or direct strength, is due to the volume of the gases. If a pound 

of a certain explosive gives, for instance, 1,000 cubic feet 

of gas when completely detonated or fired, while a pound 

Strength and of another explosive gives 500 cubic feet and a pound of a 

Quickness third gives 2,000, the lifting power of each explosive will 

be in direct proportion to its gas volume. 

But the violence of the gases depend, not on their 
volume, but on their speed. If they are comparatively slow in forming and in 
forcing their way out of their confinement they will break out large cracks 
and escape through them, pushing the material aside. If they are very fast 
or quick, they will grind and pulverize everything they come in contact with, and 
throw out the whole side of the confining material, but will not crack it so far. 

The matter can be made clear by comparing a push with a blow of a hammer. 
Both may have equal power, but the effects on a block of wood, for instance, 
at the point where they are applied are very different. The push will move 
the object almost without marking it. The blow may move it, but it is sure 
to leave a mark of greater or less depth, depending on the nature of the ham- 
mer and its speed. A still better comparison, perhaps, is that between the blow 
of a sledge and of light hammer. It is possible to hit a blow of as much power 
or weight with one as with the other, but the material at the point where the 
blow lands with the light hammer will be badly dented, or maybe broken. 
The reason is that the light hammer moves with much greater speed. 

In quarries blasters make use of these facts in order to get the rock broken 
out in pieces of the size preferred. When they want large pieces they use an 
explosive with sufficient power to break the rock, but, comparatively speaking 
with a slow speed of gases; when they want small pieces and much shattering, 
they use an explosive of the same or greater power but with swift and violent 
gas action. 

44 



For each result and for each material a certain power is required and a 
certain quickness of the gases is best. By way of illustration, take soil blasting for 
tillage purposes. There is no object in violently grinding the earth at one spot 
while surrounding earth that might be reached is left untouched. A proper 
explosive for this purpose is one that will have enough pulverizing action, 
that will lift and shake up the soil, and that extends its effects for long distances. 
For an example of the other extreme, take mud-capping rocks. For this work 
the explosive cannot be too violent in action. The gases, backed up by the 
rapidly yielding wall of air behind them, must strike the rock a crushing blow 
in the minimum of time. 

Nitroglycerin and ammonia powders and dynamites, for all practical pur- 
poses, are of equal strengths when of equal markings. The strength is indi- 
cated accurately by percentage figures. 

Nitroglycerin explosives are uniformly quicker and more violent in action 
than ammonium nitrate explosives, and the more nitroglycerin there is in the 
explosive the quicker it is. The ammonia explosives are not as quick, in any 
strength, as the corresponding nitroglycerin explosives. Therefore a 50% 
nitroglycerin powder is more violent than a 50% ammonia powder, and a 
20% ammonia powder is much less violent than a 50% grade. 

When the object is to shatter and reduce to fine fragments the material to 
be blasted, the proper explosive is a quick one, while when the object is to 
lift and shake up the material the best explosive is a slow one. (See table on 
page 47, also detailed recommendations on page 28.) But there are other 
factors that must be considered. 

Nitroglycerin explosives resist water better than ammonia explosives, but 
if the cartridge wrappings are not broken or opened, ammonia dynamite or 
powder can be loaded in wet holes with entire satisfaction. The firing should 
not be delayed any longer after loading than necessary, and it is wise to plan 
the work so that it may be done at the longest within a half hour after loading. 
Storage in a damp place will weaken explosives, especially ammonia explosives. 

Gelatin explosives resist water very well, and may be loaded in wet holes, 
or under water, with assurance that they will explode with their full power. 
Blasting gelatin is entirely water-resisting. 

Explosives will freeze, and when in this condition are dangerous, and can- 
not be fired properly, if at all, with a cap of any kind. They must be thawed 
and they must be handled very carefully if they are to be used. On no account 
attempt to cut the wrappings, to break a stick, or to handle the frozen explo- 
sive in the ordinary way. (See pages 48 and 49 for directions for thawing.) 

Regular nitroglycerin explosives are quickest to freeze. Others, known as 
"Low Freezing," will stand much lower temperatures without 
showing trouble in this respect. 
Freezing Ammonium nitrate explosives also will freeze, but not quite 

so quickly as nitroglycerin explosives. They too are made on 
both regular and low freezing formulas. The low freezing am- 
monia will stand more cold than the low freezing nitroglycerin. 

The regular explosives will freeze at temperatures of 45 to 50 degrees. 
The low freezing explosives will not freeze and become solid till the thermome- 
ter gets down to at least 25 degrees, and in practice many of them can be used 
right out in the open without any trouble when the temperature is down to 
zero and below. The length of time the powder is exposed to the cold has 
much to do with its freezing. 

The safety point for both low-freezing explosives and regular explosives 
is not a matter of rule, but of watching the explosive. When high explosive 

45 



powder or dynamite is frozen, the sticks will be hard, and when it is 
partly frozen they usually will have a mottled appearance on outside of the 
paper wrappings. The hardness may only be in spots. When not frozen, the 
sticks should be a little soft all over. No explosives should be handled much, 
cut, punched, rubbed, broken or loaded when they are frozen. They can- 
not be exploded satisfactorily and such acts are dangerous. 

In cold weather always use the low freezing grade of explosives, for the 
regular grades may freeze in the holes before they can be fired. It is a good plan 
to use the stronger caps, say No. 8 (see page 56) in cold weather. When 
a charge of explosive is chilled but not frozen it can be fired satisfactorily by a 
heavier impulse (blow and heat) than ordinary, such as a fresh No. 8 cap gives. 
The low freezing explosives do not differ in action from the regular explosives, 
and are just as efficient. 

The gases of explosives naturally are more or less objectionable when 
breathed. Some of them are poisonous, others are merely disagreeable. When 
explosives are used out in the open the gases are taken up by the air so quickly 
that none of them give any serious trouble, though they do cause headaches. 
It is only in tunnels and deep shafts where the air is confined that the matter of 
fumes is important, not on farms. 

Special explosives have been developed for tunnel and mine work, but they 
are not important in agricultural work. The only fact about fumes worth know- 
ing in farm blasting is that nitroglycerin explosives either 
in the form of their gases or when absorbed through the 
Other Properties skin will cause headache somewhat quicker than ammonia 
explosives. The so-called fumeless explosives always cost 
more than any ordinary dynamites and powders and are 
not suited to farm work. Farmers will do well to buy grades of explosives 
suited for their special purpose. 

Dynamites and most high explosive powders are light-colored materials 
that look like fine, sticky sawdust, and they always are packed in "sticks" 
made with cylinders of tough paper. These sticks vary in 
diameter and length. The standard is 13^ inches in diameter 
Appearance and 8 inches long. This is the size carried in stock by dealers 

of Explosives and in the magazines of the makers. You can get special 
sizes of sticks if you need a considerable quantity, varying 
from J4, of an inch in diameter to 4 inches. Sizes other than the standard 1 34 
by 8 inch may cost more per pound than the standard owing to higher pack- 
ing cost. 

Dynamites and high explosive powders are packed in wooden boxes con- 
taining 25 pounds or 50 pounds, as you prefer. A 50-pound box of 20% ammonia 
powder or dynamite will contain about 105, 134 by 8 i^^ch sticks. If of 20% 
nitroglycerin, it will contain about 98 sticks. If of gelatin dynamite, or blasting 
gelatin, it will contain about 88 sticks. 

A word should be said here about the cost of explosives. No quotations can 
be given because the prices vary in different parts of the country and from time 
to time. The ammonia products usually are cheapest. The cost of course 
follows the percentage strength, the low percentages cheaper and the high per- 
centages dearer. Gelatin explosives cost about the same as straight nitroglycerin 
explosives. The special explosives for use in mines, tunnels, quarries, railroad 
construction work, etc., often cost more than the explosives recommended 
here for farm work. 

In buying explosives look first to getting the one that is best suited 
to the work to be done, and aside from that the cheapest one. There 

46 



would be no object in using a straight nitroglycerin or a gelatin explosive when 
one of the ammonia farm powders would do the work, for the former explosive 
cost much more than the latter. 

To avoid "explosive misfits" it is well to consider carefully the nature of 
the material to be blasted, the conditions of weather, water, etc., and the results 
wanted. The kind of explosives to use depends on these factors. Keeping in 
mind the facts mentioned in preceding paragraphs, the reader will see that there 
is a type of explosive made for almost every condition and kind of work, and 
will understand why one will not suit the work of another. 

As the briefest and clearest way of giving general suggestions for the type 
of explosive best for different agricultural work, a table follows: (Detailed 
recommendations are given on pages 21 and 25.) 

Explosives Recommended for Different Work 

Stone blasting — mudcap Straight nitroglycerin or ammonia dynamite, 

50% or 60%. 
Stone blasting — undermine ... To break, same as for mudcapping; to throw 

out, use any dynamite or powder of 20% strength. 

Stone blasting — blockhole. . . .To shatter well, any high percentage dynamite 

or powder; to break into large pieces, 20% 
ammonia dynamite or powder. 

Soil blasting — for subsoiling 

and for tree planting.. . .20% ammonia dynamite or powder. 

Ditching— electric firing 20% to 40% ammonia explosives; (nitroglycerin 

is equally effective) ; in loose dry ground, high 
percentage nitroglycerin explosives. 

Ditching — transmitted detona- 
tion Straight nitroglycerin dynamite or powder, 50% 

strength. 
Stump blasting — in medium 
and heavy soils, wet or 

dry 20% nitroglycerin or ammonia dynamite or 

powder. 

Stump blasting — in dry sand 

and other light soil 50% nitroglycerin or ammonia dynamite or 

powder. 

If you are in doubt as to the best explosives for your particular work it is 
well to write to the manufacturer you prefer, asking which of their grades and 
brands would be most suitable. 

Detonation 

It is well known that black powder is fired by a spark, and that dynamites 
and high explosive powders cannot be fired by a spark but require a shock and 
heat. It is not so well known that there are great dif- 
ferences in the nature and effect of the explosion of any 
Firing, Exploding powder or dynamite, due to variations in the way it is 
or Detonating fired. 

An explosion of powder or dynamite is the result of 

a very sudden creation of a great volume of gas from a 

smaller volume of powder. The kind and amount of gases produced by any 

47 



high explosives depend on the kind and amount of shock used to fire the charge, 
and on its confinement. 

The effect of lighting a piece of unconfined dynamite with a piece of fuse 
without a cap on, is that the dynamite will burn fast without exploding and make 
a dense smoke which has a bad smell and produces severe headaches. This is 
simple combustion. If the piece of dynamite is confined closely and lighted in 
the same way it will explode, but will give off similar bad fumes. If a weak cap 
is used on the fuse, or the dynamite is set off by a fall, the dynamite will be 
partially detonated, and explode with considerable force, but it still will give 
off the bad fumes and smoke. The same piece of dynamite fired with a No. 6 
or 8 cap will be completely detonated, and will explode with great violence and 
force, even when unconfined, except by air, and will give off very little smoke. 

The last-named explosion is detonation. It is produced by a violent shock 
in connection with intense heat. Nitroglycerin is 5 times as strong as black 
blasting powder when exploded by fire, and 1 times as strong when detonated. 
This explains the enormous force given by detonation as compared to simple 
explosion. 

But detonation itself is no set thing that always takes place the same. 
There is good, or complete, or full detonation, and there is partial detonation. 
In case of incomplete detonation, or any detonation at a less speed than the 
greatest for any particular explosive, the gases formed are not what they should 
be. For one thing, they are more noxious or poisonous. The more powerful 
and severe the blow delivered by the cap, the more quickly does the chemical 
action take place in the explosive. It is only when high explosives detonate 
with their greatest speed that their maximum power is generated. 

Air spaces about the cap in the stick of explosive cushion its blow and weaken 
detonation. It is the nature of the initial detonation of the powder right around 
the cap which governs the nature of the explosion of the whole charge. A blaster 
should understand the importance of setting up complete detonation in order to 
get the greatest amount of force out of explosives. Sometimes explosives lose 
as much as 20% of their effectiveness when fired with weak caps. Lack of 
confinement has a similar effect. Sixty per cent, dynamite poorly detonated 
is less effective than 40 % well detonated. 

When explosives become chilled it is difficult to detonate them properly 
with the usual cap, hence the advisability of using a very strong cap in cold 
weather — a No. 8. Many of the holes are frequently loaded for some time 
before firing, and even if the powder is soft and normal while charging, it after- 
wards becomes somewhat chilled in the cold ground. 

Throughout this and other bulletins in this series, the 

terms caps and electric blasting caps are used in speaking 

Cap Means of the exploders used to fire the charges of dynamite or 

Detonator powder, although in the field and among manufacturers 

the same articles are called by the terms "detonators," or 

"electric exploders." 

Thawing Explosives 

It has been pointed out (on page 45) that regular explosives chill or freeze 
at temperatures of 45 to 50 degrees. With the increase in the number of low 
freezing explosives that seldom need thawing, the necessity for doing the 
thawing on farms is not as frequent as it used to be. 

Frozen dynamites and powders are dangerous materials, and whenever 
the temperature is near the freezing point for them, the sticks should be 

48 



Frozen Explosive 



inspected before using to see if they show any of the hardness that indicates 
chilling. If so, handle them very carefully till they are thawed. Dynamites and 
high explosive powders will be a little soft to the pressure 
of your thumb when they are not frozen. 

Frozen explosives are dangerous because they are 
very much more easily exploded in the course of ordinary 
handling. They are more sensitive to friction and to 
blows of tools. The sticks may explode when dropped to the ground or 
floor, when sticks are broken in two, when wrappings are cut with a knife, when 
cap holes are punched with a stick, or when they are shoved into a hole with a 
tamping stick. At the same time they are so much less sensitive to the direct 
shock of a detonating cap that they cannot be fired properly with a cap. 
Therefore the rule must be laid down that frozen sticks of high explosives never 
must be cut or ruptured or used until they are thawed. 

When nitroglycerin freezes it crystallizes, therefore the nitroglycerin in 
dynamite or powder tends to separate from its absorbing materials into small 
crystals. When the dynamite is thawed slowly with sticks lying on their sides, 
the nitroglycerin is reabsorbed as fast as it liquefies. But when thawed too 
fast, the nitroglycerin is liable to run out of the sticks before it is reabsorbed. 
Quick thawing will damage explosives a great deal more than they would be 
damaged by freezing followed by long, gradual thawing. 

Thawing is a dangerous operation when not done 
right. It probably is correct to state that more acci- 
dents with dynamite have occurred in the course of 
improper thawing than for all other reasons put to- 
gether. At the same time proper thawing is entirely 
safe. 

Two of the most frequent causes of accidents while 
thawing explosives are in putting the sticks into water or 
steam, and putting them on hot stoves or stones. 
Water, and especially hot water, forces the nitro- 
glycerin out of the sticks. The free nitroglycerin goes 
to the bottom, and explodes at the time of the first 
increase in heat, or first light blow. When sticks of 
explosives are laid on hot material the nitroglycerin also runs from the paper 
wrappings and drops of it fall to the stone or 
metal. This almost always causes an explosion. 
At about 350 F. degrees of heat, which is only a little 
more than that of boiling water, the nitroglycerin 
will explode without a shock. 

Examine your explosives a day or so before you are ready to use them, 
and if they show that they are frozen, proceed to thaw 
them in one of the following ways: Use only a DRY 
warmth. Use no temperature higher than is comfortable 
to the hand, or the limit may be set at 1 00 or 110 degrees. 
Use no heat of any kind that cannot be controlled with 
certainty. If you do this you will be safe. 

Every large maker of explosives will supply thawing apparatus that is 
safe. Sometimes this is a double kettle arranged so that the sticks of explosives 
can be placed in the inside vessel, while the outside vessel can be filled with 
warm water and a blanket can be spread over the top. Other more elaborate 
thawers consist of a vessel containing watertight tubes just big enough to hold 

49 




One type of thawer on 
the market. 



Causes of 
Accidental Explosions 



Safe Thawing 



sticks of explosive, running through a space to be filled with warm water. The 
catalogs describe these ready-made thawers in detail. 

Home-made thawers can be arranged with two buckets, one small enough to 
hang inside the other. Put the sticks inside the small one and warm water around 
the outside, in the big bucket. Another good way is to put a five-gallon can of 
warm water inside a barrel, or box, and pile the sticks of explosives in the barrel 
around the can. The top of the barrel should be covered with a blanket. Or 
put the water in the barrel and the explosives in a can or bucket. A small 
closet of course can be used instead of a barrel. A can of warm water can be set 
inside a magazine to keep the temperature up. 

The old-fashioned manure pile method of thawing is reliable and safe, though 
a good deal of trouble. This consists in burying a box somewhat larger than a 
box of explosives in fresh horse manure, and placing inside it the box of explo- 
sives to be thawed. A foot or more of manure must cover the box, and a small 
pipe or tube should be inserted for ventilation. The manure must be fresh. 
Allow at least 1 hours to thaw a box of dynamite or powder in this way. Twenty 
hours is better. 

The box of explosives can be taken into any warm place that is dry, but if 

this is a building you must take your own risk of fire and accident. Watch the 

box and the sticks to see if the freezing and thawing causes the sticks to leak 

free nitroglycerin. If any of this leaks out of the stick and 

gets on the floor it must be washed up according to direc- 

Sticks on Sides tions in paragraphs on storage. (Pages 59 and 60.) The 

sticks of explosives had better be piled irregularly rather 

than in tiers, for thawing. They will rise in temperature 

quicker in this way. They always must lie on their sides rather than stand 

on end. 

Electric and Fuse Firing 

The very best way to light fuse is to split the end for an inch or less, 
and stick the burning head of a 
freshly scratched match right against 
the exposed powder at the head of 
the split. This will light the fuse 
even in a strong wind. 

Where there are very many 
fuses to light in succession, as in 
subsoiling, it some- 
Fuse and times is of advantage 
Cap Firing to use a gasoline or 
other torch, holding 
the hot flame under the fuse for an instant. Whatever the method, do not 
leave till you see the fuse spitting sparks and smoke swiftly and regularly. 
Further di cussion of fuse firing, except as to its adaptations, is not needed. 
Farmers who have only a few stones or stumps to blast, 
or who are planting a few trees or doing a little subsoiling. 
Electric Firing will not need any other method of firing than by caps and 
fuse. Ditch blasting in ground not watersoaked demands 
electrical firing, while the blasting of large stumps, particu- 
larly if green, and in sandy soil, as well as the blasting of large rocks, is made 
easier and cheaper by electrical firing. For large amounts of almost any blasting 
except that of tree beds, subsoiling and very small stumps and isolated small 

50 





A good reel for leading wire. 



boulders, the purchase of an electric blasting machine and the necessary wires is 
justified by the advantages of the electric methods of firing. 

The primary reason 
for the superiority of 
electric firing over fuse 
firing is that several 
charges may be explod- 
ed at once; the different 
charges will increase 
the effi- 
ciency of 
Advantages each other. 
Thus in 
ditching, 
you can fire many 
charges in a row and 
make a perfect ditch. In stump blasting several small charges very often 
will take a stump out better than one large charge, and in orchard, and 
garden subsoiling the simultaneous blasts frequently are of advantage. 

Electric firing is more certain when the charges are under water. The 
danger from misfires due to moisture as well as from some other cause is reduced. 
Should misfire occur, you are safe in going to the charges as soon as the wire 
is disconnected from the blasting machine. With a fuse you must wait some 
hours to be safe. When several charges, as for instance, several boulder blasts 
are to be fired, you can make one trip to safety do for the lot, instead of having 
to travel back and forward for each shot. Finally, the intelligent and careful 
use of electric firing, with its possibilities of two or more small charges doing the 
work of one large one, and its other economies, will save considerable ex- 
plosives. 

All the makers of explosives supply electric blasting machines. The ma- 
chines are small boxes of wood or metal, containing a modified magneto with a 

handle on top that you either push down or pull up, 
depending on the make of machine, to operate and 
Electric Machine to fire the charges. The machines are made in vari- 

ous sizes and capacities to fire 3, 10, 30, or more 
charges at once. The 10 charge machine weighs 
about 10 pounds. Full directions for operating and caring for the machines 
always accompany them. 

For electric firing, in addition to the machine, you will need electric blasting 
caps, connecting wire and leading wire. The leading wire is copper wire large 




Duplex Leading Wire. (Actual size.) 

enough to carry the amount of current required for the number of charges to be 
fired simultaneously. It is covered with insulating material, and is made strong 

and durable to stand much use. To make the circuit from the 
Wiring blasting machine to and through the charges and back again, 

you must have two strands of leading wire. It comes from the 
51 



explosive makers in single-strand 
form, which must be doubled, and 
in what they call duplex form, which 
has two strands of insulated wire 
twisted together or wrapped to- 
gether under one cover. 

The two small copper wires that 
are fixed in the electric blasting caps 
(see page 56) should be long enough 
to reach out of the holes. They may 

be bought in a 
Electric variety of lengths, 

Blasting Caps but 4 or 6 feet 

are regarded as 

standard. If the charges are close enough together so the wires can be con- 
nected, no connecting wire will be needed; but whenever the distance between 
is more, the charges must be connected, and connecting wire is the right thing 
to do it with. There is no particular limit for the distance between charges 
that may be connected for firing together, up to 25 feet or more. 




Connecting wire comes on spools. 



A very bad connection— a cause of misfires. 




Good connection for electric cap wires 




Good connection for small cap wires and large leading wire. 

The diagrams in these pages will show how to make electric wire connections. 
Cut away the insulating on the wire ends and wrap the ends together tight. 
Wrap them for two inches. Looping the wires will not do. Be careful to 
scrape with a knife or stone the wire ends to make them bright before wrap- 
ping them together. Corroded or dirty connections are a cause of misfires. 

If the leading wire gets broken and must be 
Wire Connections spliced, solder the connection after wrapping the 

ends together, then wrap the joint with tape to 

52 




insulate it. Ordinary tire-tape is good, but a better way is to wrap the joints 
with special rubber tape under- 
neath and to cover this with the 
tire-tape. 

When only one charge is to 
be fired, connect the ends of the 
2 strands of the leading wire to 
the 2 electric blasting cap wires 
and connect the other leading 
wire end to the blasting machine 
posts. The connection with the 

Tape for wrapping joints and broken insulating. gl^ctrical blasting machine should 

be made the last thing before firing, after you are sure that the charges are all 
ready and after every person and animal is out of the way of the flying pieces. 
When the blast is all connected together ready to fire, except attaching the 
leading wire to the machine, give the handle of the machine one or two light 
strokes, to make sure that it is working smoothly and to charge the magnets. 
Then attach the leading wires to the binding posts on the machine, making 
sure that both the binding posts and the wires are bright and clean where they 
come together. Raise the handle of the machine to its full height and push it 
down with speed. When the handle starts on its downward stroke, the pinion 
immediately clutches the armature and starts the generation of current. The 
current, growing stronger as the stroke proceeds, causes considerable resistance 
toward the end of the stroke. The current generated is directly in proportion 
to the speed with which the handle is pushed down, especially just before reach- 
ing the bottom. Any let up toward the bottom will cause a drop in the current 
and may result in misfires. Therefore, make it an invariable rule, whether the 
shot be large or small, to bang the handle down hard and carry the stroke with 
all possible speed to the bottom. Try to knock the bottom out of the box. 
Machines which operate by the twisting of a handle must be handled equally 
quick. 



Very best wire connection, ready for soldering if need be. (Excellent for leading wire.) 

When more than one charge is to be fired the different charges must be 
connected together. The diagrams will help you to understand how this should 
be done. For nearly all agricultural blasting the connection in one series is the 
best — that is, connecting each charge to the next one and so on until they are 
all joined, with one loose electric blasting cap wire from the two end charges 
of the series. (See diagram A and D, page 54.) 

Once in a while, where the series is long and the charges are in a line, you 
can arrange to have the 2 loose wires at the same end of the series by making 
the connection, not to each next charge in the row, but to the one beyond and at 
the farther end doubling back and connecting the missed charge. Do not use 
this method where it involves many splices with connecting wire. 

Connections in parallel sometimes are desirable in the case of ditches, or 
other extensive blasting. To make them run a piece of wire away from one lead- 
ing wire strand along the lines of charges and connect one wire to each charge. 
Then run another similar piece of connecting wire connected to the other strand 
of leading wire, and attach to it the other cap wire of each charge. 

But to fire charges by means of parallel connections takes so much electric 
current that a blasting machine cannot be used. Generally speaking, parallel 

53 



A Sti'^ight ser-ies connecf'On for 

US& with b/asting machine 




£ Dii/i'ding into ti/vo Circuits to reduce 
'-esistarce.- used with b'asting machi, 



C Multiple -Series used with both 
blasting machine and power-current 



Method of wrapping wires together to make electrical joint, and of taping joint. 

connections require current from an electric light or power plant. If your 
work is such that the charges cannot be connected in series or that parallel 
connections are desirable, it is well to communicate with an expert or authority 
on electricity for special sugges- 
tions and advice as to how best 
to fire your charges. 

In a bulletin of this size it is 
impossible to give a comprehen- 
sive statement of 
Current electric firing. But 

Required to give some idea, 
it can be stated 
that an electric blasting cap re- 
quires 1 to 1 3^ amperes to insure 
firing. This amount of current will 
fire one cap or many in a series. 
To force this amount of current 
through the wires requires a 
certain voltage, the amount de- 
pending on the size and length of 
all the wires, and on the joints. 
One bad or poorly wrapped joint 
will increase the resistance of the 
circuit more than several caps. 
The voltage of the current re- 
quired to fire any circuit usually 
can be computed by an expert 
when the details of the wiring 
system are explained to him. 

When charges are connected 
in parallel, instead of series, or in 
multiple series (see diagram C), 
each circuit requires 1 to 1 3^ 
amperes of current. That is, each 
cap requires 1 to 1}^ amperes 
when connected in parallel. The 
voltage required, of course, de- 
pends on the resistance of the 
wires. A very much greater cur- 
rent than of 1 to 1 3^ amperes will 
do no harm; in fact it is desirable. 

Electric blasting machines 
are constructed to give a suffi- 
cient amperage and voltage for Ways of connecUng up charges for electric firing. 

54 




E Three wire system with threv-post 
blasting machine 'B' used with two-post 
\ ryjachine is better 



r. parallel connection, used with 
electric light or power-current 



\ \ \ \ \ 



^\)\ \ iw \i\ n 



r,^ 

3^>o/e.- w/nedm sen'es, m a /to/c. w/re^tn G^ fi/ckmg up separate ftofes 

/*oe so ^oo<fasfijr^//c/. para//efi tesi i*^ i/t series, not rec<ynme/7de<f. 

Q.... Combmst/ons ofpsra/Ze/ c/rcu/ts 
tvAen f/rin^ w/th e/ectric //^/^t or 
po^er current. 



3 




firing properly the number of caps specified as the capacity of the machine 
when connected in a series. If too many caps, or more than usual wiring 
is connected to any machine, misfires will result. Other current can be 
used in place of that supplied by a machine, provided it 
has enough and not too much amperage and voltage. 
Too great a current will burn out wires without firing all 
the charges. Too little current sometimes will do the 
same, or it may do nothing. In emergencies dry cells or 
wet batteries can be used by skillful operators to fire a 
few charges, when great care is taken to have the wiring 
arranged for the purpose. Before attempting to fire 
charges with batteries of any kind, learn the amperage 
and voltage of their output and see that your shots come 
within their limits. The use of batteries is more ex- 
pensive than the use of electric blasting machines. 

Bare connections at the charges or back along the 

Two post electric blasting leading wire should be raised off the ground by stones, 

machine— push down sticks or piles of dirt placed under insulated parts of the 

wires at each side of the splice. During a thunder storm, do 

not stand near any of the charges that have been connected. Avoid dragging the 

leading wire over bareor rough ground as much as possible, and particularly avoid 

kinking it. Be careful not to break or tear or scratch the insulating of any wires. 

Do not attempt to fire through a long length of leading wire wound in a coil 

or on a reel. The induction, leakage or short circuit of current in the coil 

of wire causes the blasting machine to deliver a slow discharge, which is fatal to 

proper firing. Leading wire that is watersoaked or that is covered with mud 

will lose a considerable part of its current. 

Misfires 

Nearly half of the accidents noted each year in blasting operations are the 
result of attempting to examine misfires too soon. If misfires occur with fuse 
firing, stay away from the shot at least 2 hours. It is better to wait until the 
next day, for the spark may linger 24 hours and still cause an explosion. (See 
page 42.) Rock and stump misfires are to be avoided especially. When you are 
firing the charges electrically, you may approach the shot with entire safety as 
soon as the lead wire is disconnected from the blasting machine. 

Misfires are due to the following named causes. The remedies for them are 
care in preparing the charges and in loading, the details of which are given in 
the proper chapters. 

With cap and fuse firing, misfires are caused by having the end of fuse 
pulled back a little from the bottom of the cap, by crimping the fuse too tightly 
with a groove crimp and shutting off the spark, by damp or wet fuse, especially 
at the end of the cap, by defective cap, by the cap getting pulled out of the 
explosive, by kinked, damaged, broken or pinched fuse, by failure to light fuse. 
A great many misfires were never fired at all. With electric firing the reasons 
for misfires may be damaged wires in the hole, causing short circuits, defective 
caps, overloaded blasting machine, cap pulled out of explosive, bad wire con- 
nection at some point, or broken wire. 

If you find after due time that for some reason the charge cannot be fired 
by lighting the old fuse or by sending current through the wires, you must deal 
with a real misfire. 

The best thing to do is to put in another, lighter charge in a new hole made 
6 to 1 2 inches of the original one. The explosion of the new charge will explode 

55 



the old one. Never touch the tamping in the old hole unless you know just how 
deep it is, or how many inches of it there are above the charge. Once in a 
while the tamping may be dug out of a blockhole misfire. It seldom pays to do 
this in stump blasting, and never in ditching, or soil blasting. At best it is a 
dangerous operation. Mudcap charges can be opened and new primers inserted 
without danger or difficulty. This should be done by removing part of the 
mud at another point, and inserting a new cap and fuse, or electric blasting 
cap, as the case may be. 

Cap (Detonators) 

Blasting caps are little copper tubes closed at one end, 13^2 to 2 inches long 
and something less than a quarter of an inch in diameter. At the bottom is 
placed several grains of a high explosive that is very powerful and exceedingly 
sensitive to heat, shock and friction. This high explosive usually is fulminate 
of mercury, but often is other 
material. They are packed in small 
tin boxes, open end up, usually 100 
to the box. 

The purpose of the blasting 
cap is to supply the shock and heat 
necessary to detonate the charge 
of dynamite or powder to be fired. 
If it were not for safety in handling 
blasting explosives, they all could 
be made as sensitive as the material 
in the caps. But such explosives 
would be impossible to handle 
without accident. In fact, it would 
be impossible to handle the little 
bit of explosive in the caps if it 
was not protected by the copper 
shells. Even at that caps must be 
kept free from jars and from heat 
and sparks to avoid premature 
explosion. 

The strength of caps is care- 
fully regulated by the makers to 
fire the dynamites and powders on 
the market. The explosive material 
with which the caps are loaded is such as will deliver a shock and a degree of 
heat of the strength and violence required. The caps are numbered according 
to strength. All dynamites and powders used for agricultural blasting require 
at least a No. 6 cap. If they are chilled a little, but not frozen, they require 
No. 8. It is the part of wisdom to use No. 8 caps all the time if you can get 
them. They give you a margin of strength should moisture or other causes 
weaken them in storage. 

Blasting caps must be used with fuse. And before they are inserted in the 
stick of explosive they must be fixed to the fuse properly. (See pages 36 to 38.) 
It is the spark which travels down the fuse that fires the cap. 

Electric blasting caps are made on the same principle as ordinary blasting 
caps. They have the copper tube, the explosive at the bottom, etc., but they 
differ in the way this explosive is fired. Instead of by a powder spark they are 
fired by a red-hot wire that is heated by an electric current. 

56 




D and £ are ordinary blasting caps ; F and G are 
electric blasting caps, often called fuzes. 




Electric blasting cap or fuze. 

Every electric blasting cap has fitted in it 2 small copper wires, which 
must be considered part of the cap. Down near the bottom of the cap is a deli- 
cate bridge of finer wire. The entire arrangement is held in adjustment and 
sealed by a casting of sulphur-like substance. 




The interior construction of an electric blasting cap or fuze. 

For fuse blasting you must use regular blasting caps, and for electric blasting 
you must use electric blasting caps. It is impossible to substitute one for the 
other. Never pull at the wires in an electric cap. It is dangerous and may loosen 
or throw out of adjustment the arrangement of wires inside. And never try to 
dig out the wires of an electric cap or to dig or to punch the explosive in the 
bottom of a blasting cap. 

Fuse (Safety Fuse) 

Fuse is used for firing black blasting powder and for firing dynamite and 
high explosive powders through the medium of a cap. It is made by enclosing 

within a covering a train of special 
black powder and an inflammable 
cotton string. The spark runs 
down this powder train. 

The powder used in fuse is 
specially made for the purpose, is 
pulverized and is highly compressed 
by the covering of the fuse. The 
covering itself is made of varying 
materials, depending on the condi- 
tions under which the fuse is to be 
used. For dry work it is only 
enough to hold the powder in place 
and to keep the powder train from 
getting broken. For damp and wet 
work it is made waterproof by in- 
Fuse as it comes in rolls. creasing the number of layers in 

the covering and by adding varnish, coal tar, as other waterproofing material. 
There are many brands of fuse on the market. In buying fuse you must 
bear in mind the character of your work. For work that is en- 
Grades tirely dry you can use ordinary cotton or hemp fuse with satis- 
faction, if it is large enough to fit a blasting cap snugly. 
For work in damp ground, use a fuse in which the cotton or hemp is covered 
with one layer of waterproof tape or other material. This is called single-tape 
grade or may be known by brand name only. For work where the ground is 
wet, such as in stump and stone blasting in damp or wet weather, use a double- 
covered fuse — fuse that has two layers of tape or other material over the cotton 

57 




covering and waterproofing material added. For work where water covers the 
charges it is best to use fuse with three layers of tape or other material and 
full waterproofing. This is called triple-tape fuse or may have special brand 
names. When buying fuse for general farm work, it is well to get a water- 
proof grade, since it can be used for both wet and dry work. 

Most reliable fuse burns about 2 feet per minute when in perfect condition. 

If it becomes damp, it burns much slower. Cases have been known 

where the spark smouldered in damp fuse for hours without 

Rate of traveling more than a few inches. Another source of uncertainty 

Burning is where fuse has been pinched. It may take the spark a minute 

or an hour or a day to get past the pinched point. 

When fuse is cold, it is hard and brittle, and may crack open 
when unrolled. If it gets too warm, its waterproofing material may penetrate 
to the powder train inside and ruin it; or the covering may first soften and then 
harden, in this condition breaking as though cold when unrolled. If grease is 
allowed on the cover it may combine with the waterproofing and ruin the 
powder inside. 

Handling Explosives 

Dynamites and powders in boxes can be hauled freely in spring wagons. 
You should see that no bolt heads or other metal parts project from the wagon 
boxes to strike the boxes of explosives. Sweep all dirt out of the wagon. Have 
the beds clean or covered with straw or blankets. 

Go over your wagon and harness before you load dynamite to make sure 
they will not break down while you have the explosive aboard. Be sure you 
have the hitching straps or tie-ropes along, and do not leave the horses standing 
without tieing them securely. Break no colts while hauling explosives. If 
you use a motor, stop it and set the brake tight before you leave the load. 
In driving through a town stay away from dangerous crossings. 

Keep the sticks of explosive in their original boxes until you are ready to 
use them. Don't have them around loose. In carrying them to the field, use 
a wood basket or a box and not a metal bucket. Always protect explosives from 
all possibility of being reached by falling sparks or from match heads or other 
source of fire. Rain, hot sun and the like must be kept away from explosives. 
Use care to lay sticks or set the boxes or baskets containing explosives where they 
will not fall down, be blown over by wind or knocked over by careless people 
or by animals. Cattle will eat sticks of dynamite, or powder, because of their 
sweet and salty taste. The explosive will make them sick, sometimes kill them. 

Since nitroglycerin often will cause headache when absorbed through the 
skin it is best to wear gloves when handling the sticks. For this same reason 
some people punch holes for caps in the sticks with a piece of wood rather than 
with the handle of the cap crimper. 

Caps should not be carried in the same basket or box as explosive, but should 
be carried separately. Take only enough along to do the work in view and 
carry them in the tin boxes they come in. Many serious accidents have been 
caused by blasters having loose caps in their pockets during work or afterwards. 
Sooner or later a chance jar is likely to set them off. When several caps have 
been taken out of the little tin box in which they come the rest will be loose and 
will rattle about. This should be stopped by filling up the empty space with 
paper. 

The handling of caps is not dangerous provided you do it intelligently and 
with care. Keep them safe from any jars or heat. You can sometimes do 

58 



many foolish things with dynamite and powder without 

serious results to yourself, but not with caps. Letting a cap 

Handling fall to the ground or floor likely will cause it to explode. For 

this reason you should keep the caps and explosives apart, 

in hauling, storing, and handling, bringing them together 

only at the last minute before you prepare the charge to be loaded in the hole. 

One cap can produce an explosion powerful enough to tear your hands off. 

Electric blasting caps must be handled with the same care as regular 
blasting caps. All caps must be protected from dampness during handling. No 
trouble will be experienced if you use common sense at every turn, but thought- 
lessness and carelessness in the handling of explosives will cause disaster. Bear 
in mind that when an accident happens with an explosive there is no time to 
save yourself, and no afterthought will prevent serious injury to you. Fore- 
thought is the thing with explosives. In an explosive you are handling an enor- 
mous strength. The fact that it occupies small bulk now should not interfere 
with your imagining it as an enormous engine with power enough to crush you 
easily, but under entire control if you do your part right. 

Storing Explosives and Supplies 

The storing of dynamites and powders on farms offers no serious problems, 
though it may call for some shifting of arrangements to meet proper require- 
ments. The explosive must be kept dry. They should be kept cool. This means 
that any ordinary temperature of the air is all right, except that in hot weather 
the room where the explosive is kept should not get warmer than 80 or 90 
degrees. If it is properly ventilated day and night it will not. Probably the 
best common storage place for explosive is in an outbuilding under the floor of 
which the air circulates freely and with a ceiling between the room and the roof. 
It should be strong, and should be provided with a lock. A responsible person 
should have charge of the key at all times. 

The explosive should not be kept in a garret, because the hot sun beating 
down on a roof will raise the temperature under the roof away past the 100 
degree mark. 

Dampness is injurious to explosives, as noted on page 34, and dynamites 
and powders must be kept where moist air will not surround them. The ideal 
storage would be fireproof, but since this is out of the question on the average 
farm, the best that can be done in that respect is to guard against fire. It is 
well to make sure that the explosive is out of reach of any stray or malicious 
bullet that might be fired into it. 

Look to your insurance policies and see whether they provide against the 
storage of explosives in any of your buildings. Store the explosive in a building 
not covered by the insurance. 

Where large quantities of explosives are to be stored as a regular thing, 

or for any length of time, it is advisable to consult the makers 

of explosives or others experienced in their handling in regard 

Magazines to the location and construction of a magazine. A magazine 

can be set up cheaply and can be made fireproof, bullet proof, 

thief proof, well ventilated, dry and safe in every way. It 

should be built of brick. Any explosive maker will furnish plans without 

charge. In any case explosives should be stored at least 50 yards away from 

any other buildings and from roads or railroads. 

59 



Blasting caps of any kind must not be stored with dynamite or powder. 

Fuse is not explosive and can be stored with dynamite or powder. 

p Blasting caps are even more subject to damage by moisture than 

" explosive and must be stored accordingly. Caps must not be allowed 

to become heated. 

A statement of the ways in which explosive deteriorates will help in 

selecting a proper storage place for it. In temperatures higher than 80 degrees 

troubles may begin. Long continued temperatures of 

90 to 100 degrees may cause the nitroglycerin to leak 

Deterioration out of the absorbing material and to gather inside the 

wrapping on the lower side of the sticks, or may even 

cause it to leak out of the wrappings through the 

boxes and to the floor. 

Strict watch should be kept of the sticks and the boxes to catch any such 
condition. If leakage occurs, turn the explosive over and reduce the temper- 
ature. Burn the empty boxes one or two at a time out away from buildings, 
and scrub the floor where the leakage occurred with a strong solution of sal 
soda. This will decompose the nitroglycerin. If it becomes necessary to de- 
stroy a little explosive without detonating it, the job can be done by immersing 
it until dissolved in such a solution, stirring it gently with a wood paddle. 

If the sticks feel smeary it is possible they are leaking. The test is to lay 
them on white paper for a little while. If they are leaking they will stain the 
paper, otherwise not. 

At a temperature of 105 degrees nitroglycerin explosives will lose 10% of 
their strength in a few days by evaporation. Repeated freezing and thawing 
is bad for explosives, especially if the thawing is rapid. Slow thawing will not 
damage them much. After explosive once is frozen and thawed, it will freeze 
much easier again. 

When stored for many months explosives are liable to decomposition of 
some of their elements, especially if they get damp or too warm. One of the 
marks of this is greenish stains inside the stick wrappings. No length of time can 
be stated for the keeping of explosives, because it practically all depends on 
conditions. Under favorable conditions most dynamites and powders will re- 
main in good shape for years. Again, a month of improper storage will ruin 
them and make them dangerous to handle. They develop troubles sooner in 
the light than in the dark. 

Deteriorated explosives are likely to be dangerous — far more so than normal 
explosive. Keep watch over what you have in stock. Maintain proper conditions 
as far as possible, but if they show troubles do not hesitate to condemn them. 

Shipping Explosives 

The shipping of high explosives is controlled by the Interstate Commerce 
Commission, and the rules and regulations are very strict and rigid. Most of 
them are embodied in an Act of Congress of March 4, 1 909, and violations are 
punishable with fines of not more than $2,000, or imprisonment for not more 
than eighteen months, or both. The person making the shipment is 
responsible. 

A copy of the rules and regulations can be secured from the Bureau of 
Explosives, Underwood Building, New York City, or can be read at any freight 
station where there is an agent. 

The rules provide that no explosives (other than certain exceptions named) 
shall be carried on any train, boat, trolley, or other vehicle carrying passengers 

60 



for hire, and that no explosives under deceptive or false markings or under- 
standing shall be delivered to a common carrier; and further, that all other 
regulations shall be complied with. 

In shipping by railroad no caps or detonators of any kind can be sent in 
the same car with explosives. In practice the railroads usually send them by 
another train, which works out to be another day in the cases of nearly all 
shipments. This is responsible for some delay in delivery of explosive ship- 
ments. Do not expect to have explosives come through as quickly as you would 
other freight. 

Explosives cannot be shipped by express or by mail, but are sent by 
freight, the same as groceries or dry goods. The railroad company is required 
to place the packages in a certain way inside the car and to brace them with 
lumber. In case of car-lot shipments the shipper must furnish this lumber and 
do the bracing. 

The regulations provide that railroads must have 24 hours' notice of ship- 
ment of explosives, and that shipments must be remoced from the receiving station 
within 24 hows of their arrival there. The packages must be plainly stenciled 
with the name of shipper and consignee, and bills of lading must conform with 
certain specifications. 

Empty boxes which once have contained explosives must never again be 
used for shipments of any kind. Farmers who have attempted to ship vegetables 
or other farm products in such boxes have unwittingly gotten themselves into 
trouble on account of this regulation more than once. 

Danger and Safety 

Modern explosives have been developed to the point where they need not 
be feared by anyone who handles them intelligently. Speaking in a comparative 
way, they may be used with no greater dangers than there is in the using of 
horses, mowers, traction engines, sawmills, or other farm equipment, or than 
there is in using shotguns or rifles. 

The general use of explosives on farms is so new that many people dis- 
trust them more because of their newness than from a clear understanding of 
any actual dangers their use may hold. A review of what the dangers are may 
help users of explosives to avoid them, and may help to build up the reader's 
belief in the safety of explosives. 

There is some danger in the handling and transporting of explosives, but 
it depends very largely on the exposure of the dynamite or powder to heat, 
flame, sparks, blows and friction. The directions say to keep explosives dry, 
to keep them at a temperature less than 90 or 100 degrees F., to keep them 
safe from sparks, and to avoid blows and shocks. If these directions are followed 
there will be few accidents. 

Probably the most common cause of accidents with explosives lies in 
violation of some of these primary rules while thawing frozen sticks of dynamite 
or powder. Freezing makes the high explosive less sensitive to the simple 
direct shock of a blasting cap, unaccompanied, as it is, by any friction. But at 
the same time freezing makes the explosive more sensitive to friction in any form. 

For this reason, though a frozen stick of dynamite cannot be fired properly 
by a blasting cap, it is very likely to be fired prematurely by a chance light 
blow from any object touching it, by your slitting the wrapping paper with a 
knife, by breaking the stick in two, or by attempting to punch a hole into it to 
insert a cap. (These operations are entirely safe when the explosive is normal.) 
If the stick is dipped in warm water or exposed to steam, or is laid on anything 
which is warmer than about 125 degrees, free nitroglycerin likely will leak out 

61 



and fall in drops. And one drop of nitroglycerin falling only a few inches may be 
exploded itself and may explode all dynamite that is near it. 

Throughout the entire course of handling the explosive, from the freight 
station to the hole in the stone or the ground, you should remember the five 
cautions which will be repeated: Keep it dry, keep it cool, keep it away from 
sparks and flame, and keep it safe from blows and friction. Be careful — as 
careful as you would in driving a big automobile or a traction engine. Then 
you will be secure from any accidents, and explosives will be entirely safe to 
handle. 



62 



INDEX 

Page 

Accidents 49, 50 

Amount of explosives required, blockholing 28 

Amount of explosives required, mudcapping 17 

Amount of explosives required, undermining 21 

Augers, Soil 31 

Bedding planes of rock 7 

Blasting boulders by blockholing 23 

Blasting boulders, general II, 12 

Blasting boulders by mudcapping 14 

Blasting boulders by undermining 19 

Blasting compared with other methods 11 

Blasting machines 5 1 , 54 

Boulders, Nature of 4, 7, 9 

Boxes of explosives 46 

Breaking sticks of explosives 37, 38, 39 

Breaking ledges 29 

Blockholing 1 1, 23 

Blockholing, results 30 

Building stone 5, 16, 31 

Burying boulders II, 14 

Buying explosives 46 

Caps, Blasting ; 56 

Caps and fuse firing 33, 42, 50 

Caps and fuse. Putting together 34, 37 

Caps, inserting in charge 17, 37, 38 

Caps, Position in sticks of explosive 36, 37, 38. 41 

Carrying explosives 33, 58, 59 

Cautions 19, 23. 32, 50, 60. 61 

Charge, What it is 33, 41 

Charges, Placing 16. 20. 23, 28 

Charges, Using two or more on one stone 1 9, 23, 29 

Chilled explosive 45, 48. 49 

Choice of methods 11. 12 

Cold weather blasting 45, 48 

63 



Page 

Combinations of methods 19, 23, 29 

Churn drills 25 

Connections, Wire 52, 53, 54 

Conglomerate boulders 9 

Cost of explosives 46 

Cost 4,5, 11, 18,26, 27 

Crimping caps 34, 35, 36, 37 

Current required to fire charges 54 

Cutting sticks of explosives 37, 38, 39 

Danger 5. 23, 32. 61 

Description of rocks 7, 10 

Deterioration of explosives 60 

Detonation 47 

Detonators 48, 56 

Differences in explosives 43, 44, 45 

Digging out boulders 14 

Dimension stone or pieces 16 

Disposal of broken rock 31 

Drilling machine 26 

Drilling, Rates of 27 

Drilling rock 1 1 , 23. 24, 25, 26 

Drilling rock, cost 26 

Dynamite. Amount required for blockholing 28 

Dynamite, Amount required for undermining 21 

Dynamite, Amount required for mudcapping 18 

Dynamite, General pioperties of 43, 46 

Dynamite, Grades and types on market 43, 44, 45, 46 

Dynamite, Kind and grade best 18. 21, 28 

Dynamite, Kinds to use, table 47 

Dynamite, Low-Freezing 45 

Dynamite. Removing wrappings from sticks 28, 33, 34, 38. 39 

Electric blasting caps 41, 48, 52, 55, 56, 57 

Electric blasting caps. Inserting in sticks 36, 37, 38, 41 

Electric firing 50, 51, 55 

Electric firing. Directions for 19, 29, 41, 50 

Electric firing. Machine for 5 1 , 55 

Electric firing. Wiring required for 52, 54 

64 



Page 

End priming 38, 41 

Explosives, Amount required for mudcapping 17 

Explosives, Amount required for blockholing 28 

Explosives, Amount required for rolling out boulders 21 

Explosives, Amount required for undermining 21 

Explosives, Frozen 45, 48 

Explosives, How to use to lessen labor 31 

Explosives, Kind and grade required 18, 21, 28, 47 

Explosives, Low-Freezing 45, 46 

Explosives, Names of 43, 47 

Explosives, Quickness of 44 

Explosives recommended for various work 47 

Explosives, Removing wrappings from sticks 38, 39 

Explosives required. Amount per charge 17, 21, 28 

Explosives, Strength of 44, 45. 46, 47 

Explosives to use 46 

Explosive ingredients 43 

Fire breaking of boulders 11, 14 

Firing charges, Blockhole 29 

Firing charges, Mudcap 17, 19 

Firing charges. Undermine 1 9, 20 

Firing, Electric 50, 55 

Freezing of explosives 45, 46, 48 

Fumes 46 

Fuse and caps, Firing 33, 42, 50 

Fuse and caps, Putting together 34, 35, 36, 37 

Fuse cutting 34, 35, 37 

Fuse, Fastening to sticks 36, 37, 38 

Fuse, Length to use 34 

Fuse, Lighting ! 4 1 , 50 

Fuse, Rate of burning 1 9, 34, 58 

Fuse, Safety 57 

Fuzes, Electric 41, 56, 57 

Fuzes, Priming with 37, 4 1 , 42 

Gases -, 46 

Granite boulders 9 

Gypsum ledges and boulders 8 

Hammer drills 23 

65 



Page 

Handling explosives 58 

Hangfires 42 

Hardness of rock 7 

Hauling explosives 58 

Hauling rock II, 14, 31 

Headache 46, 58 

Holes for caps in sticks of explosives 38 

Holes for charges, Making in ground 20 

Holes for charges, Enlarging at bottom 20 

Holes in field, Filling 31 

Holes in rock. Drill sizes 24 

Ingredients of explosives 43 

Inserting caps 20, 33 

Joints in rock 7, 15, 23 

Labor required 12, 1 8, 22, 26 

Ledges 4. 9, 29 

Length of fuse 34 

Lighting fuse 4 1 , 50 

Limestone boulders and ledges 8 

Loading charges, Blockholing 28, 39, 40 

Loading charges, Mudcapping 17, 39, 40 

Loading charges, Undermining 20, 39, 40 

Locating charges in blockholing 23 

Locating charges in mudcapping 7, 1 5, 16 

Locating charges in undermining 20 

Loss from boulders 4, 5 

Low-freezing explosives 45 

Machine drilling 26, 27 

Magazines 59 

Making holes for charges 20, 24, 25 

Marble boulders 10, 23 

Men required 1 1. 22. 31 

Methods. Choice of 1 1, 12, 13, 14 

Misfires 32, 42, 55 

Mudcap. The 17 

Mudcapping and other methods combined 19 

Mudcapping charges. Loading 16 

66 



Page 

Mudcapping, General 11, 15 

Mudcapping results to be expected 19 

Names of explosives 43, 47 

" Niggerheads " 4 

Powder, Amount per charge foi blockholing 28 

Powder, Amount per charge for mudcapping 17 

Powder, Amount per charge for undermining 21 

Powder, Best to use 47 

Powder, General properties of 46 

Powder, Grades and types of 43, 44, 47 

Powder. Loading 16. 20, 33, 37, 39, 42 

Powder, Low-Freezing 45 

Plug and feather breaking |] 

Porphyry, Boulders 10 

Power drilling 26 

Priming charges 1 7. 20, 33 

Priming sticks of powder 33, 35, 37. 38, 4 1 

Probing about boulders 20 

Protection of explosives 33, 58, 59 

Punching sticks for caps 37, 38 

Quarrying 30 

Quartz 10 

Quickness of explosives 44 

Rock, Classes 7, 8, 15, 23 

Rock, Disposal of broken 31 

Rock, Nature 9 

Rod tamping 39 

Rolling out boulders 15 

Safety 61 

Safety fuse 57 

Sandstone 9 

Seams in rock 7, 15, 23 

Selling rock 31 

Series wire connections 54 

Shale ledges and boulders 8 

Sharpening drills 25 

Shipping explosives 60 

67 



Page 

Side priming 36, 4 1 

Slate 8 

Sledging 11, 14 

Slitting stick wrappings 38, 39 

Soil auger 31 

Spoiling of explosives 60 

Space occupied by boulders 3 

Springing holes 20 

Sticks of explosives, Number required 18, 21, 28 

Sticks of powder 46 

Sticks of powder. Breaking or cutting 38, 39, 40 

Storing explosives 59 

Strength of explosives 44, 45, 46, 47 

Talc ledges and rock 8 

Tamping 22. 32. 39. 40 

Tamping rod 39 

Tape for wires 53 

Tempering drills 25, 26 

Test loadings 1 7. 23 

Thawing explosives 48, 49 

Time required 11, 1 8, 22. 26 

Time required for blasting 22. 27 

Time required for drilling 26 

Tools 18, 22, 27, 31. 34, 55 

Toughness of rock 7 

Tractor farming 5 

Trap rock 9 

Undermine blasting 11. 19 

Undermine charges 20 

Violence of explosives 44, 45 

Waterproofing charges 36 

Weakening of explosives 60 

Weather conditions 45. 46. 48 

Weeds 5 

Wire connections 52, 53, 54 

Wire for electric blasting 5 1 , 52, 53 

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